Title of Invention

A HUMANIZED OR CHIMERIC MONOCLONAL ANTIBODY OR FRAGMENTS THEREOF SPECIFIC FOR ALPHA-FETO PROTEIN

Abstract

Abstract The present invention provides humanized, chimeric and human anti-alpha-fetoprotein antibodies, fusion proteins, and fragments thereof. The antibodies, fusion proteins, and fragments thereof, as well as combinations with other suitable antibodies, are useful for the treatment and diagnosis of hepatocellular carcinoma, hepatoblastoma, germ cell tumors carcinoma and other AFP-producing tumors.

Full Text

1. Field of the Invention The present invention relates to humanized, chimeric and human alpha-fetoprotein (AFP) antibothes, particularly therapeutic and diagnostic ccnjugates of humanized, chimeric and human fonns. In particular, the invention includes Immu31 antibothes and metfiods of treating hepatocetlulaF carcinoma, germ cell tumors, and other AKP - producing tumors using humanized, chimeric and human antibody fomis. The present invention also relates to antibody &sion proteins or fragments thereof comprising at least two Immu31 MAbs or fiagments theieof or at least one Immu31 MAb or fiagment thereof and at least one second MAb or fragment thereof other than the Immu31 MAb or fragment (hereof. The humanized, chimeric and human Immu31 MAbs» frapnents thereof and antibody fusion proteins thereof or fi-agments thereof, may be administered alone, conjugated to diagnostic and/or therapeutic agivts, in combination with a therapeutic or diiostic inamunoconjugate, in combination with ottier naked antibothes, or with at least one therapeutic agent and/or dinostic agent The present invention fiirther contemplates DNA sequences encoding humanized, chimeric and human Immu31 antibothes and fr-ments thereof, antibody iiision proteins and fragments thereof, vectors and host cells containing the DNA sequences, and methods of making the humanized, chimeric and human Immu31 antibothes. 2. Background Monoclonal antibothes (MAbs) have wide diagnostic and tberutic potentials in clinical practices against cancer. Early clinical trials revealed encouraging results using radiolabled MAbs for the diagnosis/detection (radioimmunodetection: RAID) and treatment (radioimmimotherapy: RAIT) of malignancies in cancer patients (Goldenbergera., (1993) {Intl. J. Oncol. 3:5-11; Goldenbei et al, (1995) Immmol Today 16:261-264; Goldenberg (1993) Ain. J. Med. 94:297-312; GoWenberg(1991)rfv. £xp. Med Biol, 303:107-117). Monoclonal antibothes play a central role in cancer immunotherapy, either in naked forms, or as conjugates to cytotoxic agents, such as radioisotopes, drugs, toxins, or prodrug-converting enzymes (Goldenbei et al. (1993) Immunol. To, 14:5-7). These approaches are under active evaluation, with different levels of developmental and clinical successes. Naked MAbs potentially may achieve clinical responses by inducing a cytotoxic effect upon binding to cell surice proteins that are over-expressed on cancer cells. Stuthes have shown that these thenutic ejects were accomplished by controlling tumor growth via programmed cell death (apoptosis), or by the induction of anti-tumor immune responses (Cragg efo/., (1999) Cwrr. Opin. Immunol 11:541-547). TTie majority of clinically interesting antibothes were raised in mice.. The problem of immunogenicity of murine MAbs in humans has been the major obstacle preventing their clinical application, especialy in cancer therapy vthere laie doses and repeated administrations are required to achieve maximum efBcacy. It has been demonstrated tiiat significant hmnau-anti-mouse antibody (HAMA) responses were detected in approximately 50% of patients after a single injection of muriiK MAb; greater than 90% of pateints developed HAMA following two or three repeated injections (Sears et aL, (1984) J. Biol. Response Med 3:138-150; Reynolds et al. (1989)/«/. J, Rad. Appl Instrum. B, 16:121-125; Shawlere/a/. (195) J. ImmimoL, 135:1530-1535; Jaffers et al., (1986) Transplantation, 41:572-578). hi addition, the thenutic effects of tiiese murine MAbs in humans, if any, are iiirther mitigated with their short serum half-lives and inabilities to recruit human effector cells, such as complement-fixing cytotoxic T cells. With the advent of molecular engineering, we can now genetically modify the stmcture of an antibody without affecting its antigen specificity to minimize or eliminate the HAMA responses and simultaneously enhance its immune effector fiinctions. The processes are called chimerization and humanization. These modified MAbs have been shown to possess attributes essential for enhanced clinical utility, i.e., decreased immunogenicities, longer serum half-lives in human, and the ability to recruit effector fimctions. Alpha-fetoprotein (AFP) is a serum protein normally found at significant levels only in fetal blood. In adult blood, increased alpha-fetoprotein levels are associated with liver regeneration and certain carcinomas, such as hepatocellular carcinoma, hepatoblastoma, and germ cell tumors. Hepatocellular carcinoma (HCC or malignant hepatoma) is one of the most common cancers in the world, especially in Asia, certain parts of Afiica, and is increasing in mcidence in the West, probably leiated to the increased frequency of hqjtatis infections. Accordingly, there remains a need to develop new methods and approaches to treating HCC and other s\K;h cancws. The present invention relates to murine, chimeric, humanized and fiiUy human anti-alpha-fetoprotein antibothes and fragments thereof, particularly monoclonal antibothes (MAbs), tiierqieutic and detection/diagDostic inunimoconjugates, and frision proteins comprising at least one anti-AFP antibody or firment thereof. Also contemplated herein are metiiods of diagnosing/detecting or treating a cancer using humanized, chimeric and fiiUy human anti-AFP antibothes. The humanized, chimeric and fully human anti-AFP antibothes and fragments thereof, and antibody frision proteins and fragments thereof may be administered alone, as a therapeutic and/or diagnostic/detection conjugate or in combination with a therapeutic immunoconjugate, witti other naked antibothes, or with otiier tiierKutic agents or as a diagnositic/detection conjugate. ST3MMARY OF THE INVENTION The present invention provides a monoclonal antibody (MAb) or fragment (hereof tiiat binds an alpha-fetoprotem (AFP) antigen. Preferably, the anti-AFP antibody or fragment thereof is an tnmu31 antibody or fragment thereof, as defined below. Also preferred, the anti-AFP antibody or fragment thereof is a chimeric, frilly human, mouse or humanized antibody or fragment tiiereof. Most preferably, the AFP antibody or fragment thereof is a humanized antibody or fragment thereof In. a preferred embodiment, the humanized anti-AFP or Immu31 antibody or fragment thereof comprises the complementarity-determining regions (CDRs) of a light and heavy chain variable regions of a murine anti-AFP MAb and the framework (FR) regions of a light and heavy chain variable regions of a human antibody, and the light and heavy chain constant regions of a human antibody, wherein the CDRs of the light chain variable region of the humanized anti-AFP MAb comprises CDRl comprising an anuno acid sequence of KASQDINKYIG; CDR2 comprising an amino acid sequence of YTSALLPand CDR3 comprising an amino acid sequence of LQYDDLWT; and the CDRs of the heavy chain variable region of the humanized anti-AFP MAb comprises CDRl comprising an amino acid sequence of SYVIH; CDR2 comprising an amino acid sequence of YIHPYNGGTKYNEKFKG and CDR3 comprising an amino acid sequence of SGGGDPFAY. In another embodiment, the humanized anti-AFP or Immu31 antibody or fiagment thereof comprises at least one amino acid substituted from the corresponding position of the FR of the murine anti-AFP antibody or fragment thereof. Preferably, the murine amino acid from the murine anti-AFP MAb or fragment thereof is at least oi amino acid selected from the groi consisting of amino acid residue 5,27,28,30,46,48,66, 61 and 94 of tiie murine heavy chain variable region of Fig. 4 A. Also preferred, tlK mmine amino acid from the murine anti-AFP MAb or fragment thereof is at least one amino acid selected from the group consisting of amino acid residue 4, 39,48,49, 58, 69,100 and 107 of the murine light chain variable region Fig. 4B. Most preferably, the anti-AFP antibody or fragment thereof comprises the Immu31 VK nucleotide sequence of figure IB. Also preferred, the anti-AFP antibody or fragment thereof comprises the Immu31 VH nucleotide sequence of figure 1 A. In another embodiment, the humanized Immu31 antibody or fragment thereof comprises the hlmmu31 VR nucleotide sequence of figure 5B. Still more preferably, the Immu31 antibody or fragment thereof comprises a hlmmuS 1 VH nucleotide sequence of figure 5 A. Another embodiment is a CDR-grafted humanized heavy chain conrising the complementarity determinii regions (CDRs) of a murine Immu31 MAb and the framework region of the heavy chain variable region of a human antibody and the heavy chain constant region of a human antibody, wherein the CDRs of the heavy chain variable region of the humanized anti-AFP MAb comprises CDRl comprising an amino acid sequence of SYVIH; CDR2 comprising an amino Ewid sequence of YIHPYNGGTKYNEKFKG and CDRS comprismg an amino acid sequence of SGGGDPFAY. Similarly, a CDR-grafted humanized light chain comprising Qte complementarity determining regions (CDRs) of a murine Immu31 NfAb and the frameworic region of the light chain variable region of a human antibody and the light chain constant region of a human antibody, wherein the CDRs of tiie light chain variable region of the humanized anti-AFP MAb comprises CDRl comprising an ammo acid sequence of KASQDINKYIG; CDR2 comprising an amino acid sequence of YTSALLP and CDR3 comprising an amino acid sequence of LQYDDLWT, is also described herein as an additional embodiment In a preferped embodunent, the anti-AFP or ImmuS 1 fragments of the present invention are selected from the group consisting of Fv, F(ab')2, Fdj* and Fab. Also contemplated herein is a diagnostic/detection or therapeutic immunoconjugate comprising an antibody component that comprises any one of the anti-AFP or ImmuS 1 MAbs or fragments thereof of tiie present invention, or an antibody fiision protein or fragment thereof that comprises any of the anti-AFP or Immu31 antibothes or fRments thereof of the pcesMit invaition, whaein the antibody component is bound to at least one diagnostic/detection agent or at least one therwutic agent Preferably, the diagnostic/detection or therapeutic agent of the immunoconjugate according to the present invention is bound to said MAb or fi3.gment thereof by means of a carbohydrate moiety. In one embodiment, the diagnostic/detection immunoconjugate comprises at least one photoactive diagnostic/detection agait, such as a chromagen or dye at least one radionuclide with an energy between 20 and 10,000 keV, such as a ganima-, beta-or a positron-emitting isott, a contoist ent, such as a radiopaque compound, a paramagnetic ion, including chromium (III), manganese (II), non (III), iron (II), cobalt (II), nickel (II), copper (11), neodymiura (HI), samarium (HI), ytterbium (EH), gadoimium (III), vanadium (II), terbium (III), dysprosium (QI), hohnium (HI) and erbium (HI), or an ultrasound-enhancing agent, including a liposome that is conjugated to a humanized ImmuS 1 or fragment thereof. The radiopaque compound may be selected fiwm the group consisting of iodine compounds, barium compounds, gallium compounds and thallium compounds. In another embodiment, the diagnostic/detection described herein is used in intraoperative, endoscopic, or intravascular tumor detection/dinosis. Also contemplated herein is a therapeutic immunoconjugate comprisii a therapeutic agent that is selected from tiie group consisting of a radionuclide, boron gadolinium or uranium atoms, an immunomodulator, such as cytokine, a stem cell growtii factor, a lymphotoxin, such as Uimor necrosis fector (TNF), said hematopoietic factor is an interleidan (IL), said colony stimulating fector is granulocyte-colony sthnulating factor (G-CSF) or granulocyte macrophe-coiony stimulating factor (GM-CSF)), said interferon is interferons-cc, -p or -y, and said stej cell growth factor is designated "SI fector," a hematopoietic factor, a colony stimulating fector (CSF), an interferon (IFN), a stem cell growth fector, erythropoietin, thrombopoietin, an antibody and a combination thraeof, a cytokme, t hormone, a hormone antagonist, an en2yme, an enzyme inhibitor, a photoactive therutic agmt, a cytotoxic drug, such as antimitotic, alkylating, antimetabolite, angiogenesis-inhibiting, apoptotic, alkaloid, COX-2-inhibiting and antibiotic agents and combinations thereof, or cytotoxic toxin, such as plant, microbial, and animal toxins, and a synthetic variation thereof, an angiogenesis inhibitor, a different antibody and a combination thereof. In a preferred embodiment, the cytokine is selected from the group consisting of IL-1, IL-2, IL-3, IL-6, IL-10, IL-12, IL-18, interferon-y, TTJF-a and a combination thereof, the radionuclide is selected from the group consisting of an Auger emitter, a beta-emitter and an alpha-emitter, such as P-32, P-33, Sc-47, Fe-59, Cu-64, Cu-67. Se-75, As-77, Sr-89. Y-90, Mo-99, Rh-105, Pd-109, Ag-lU, 1-125,1-131, Pr-I42, Pr-143, Pm-149, Sm-153. Tb-t61, Ho-166, Ei 169, Lu-177, Re-186, Re-I88, Re-189, Ir-194, Au-198, Au-199, Pb-211, Pb-212, ant Bi-2I3, Co-58, Ga7, Br-80m, Tc-99m, Rh-103m, Pt-109, fri-l 11, Sb-119,1-125, Ho-161, Os-189m, h:-192, Dy-152, At-211, Bi-212. Ra-223, Rn-219, Po-215. Bi-211 Ac-225, Fr-221, At-217, Bi-213, Fm-25S, B-10, Gd-157, U-235, and combinations thereof. Preferably, the radionuclide has an energy between 20 and 10,000 keV. In another embodiment, the therapeutic agent conjugated to the anti-AFP or Iramu31 antibody or fragment thereof is a photoactive therapeutic ent, such as a chromogen or dye. Considered in the present invention also is a multivalent, multispecific antibody or fiugment thereof comprising one or mote antigen bindii sites havic affinity toward an AFP target antigen and one or more hapten bindii sites havii affinity towards hen. Preferably, the anti-AFP or Immu31 antibody or fragmail thereof is humanized. Also preferred, the antibody or fiagment thweof is fiJly human or chimerized. In one embodiment, the multivalent, multipsepcific antibody or foment thereof comprises a dtagoostic/detectioa or therapeutic agec Also considered in the present invention is an antibody ion protein or fragment tlKreof comprising at least two anti-AFP MAbs or fragmmte thaeof wherein fee MAbs or fragments tiiereof are selected &om any of the anti-AFP or Immu31 monoclonal antibothes or fragments thereof of the present invention. Ina similar vein, an antibody fusion protein or fragment thereof comprisii at least one first anti-AFP MAb or fiagmait thereof of any one the anti-AFP antibothes or figoiits th:eof of the present iaventioo, and at Least one second MAb or fragnusit thereof other than any one of the anti-AFP MAbs or fragments thereof of the present invention, is also contemplated. In a preferred embodiment, the second MAb is a carcinoma associated antibody. In another preferred embodimit, the antibody frision protein or fragment thereof fiuther comprises a diagnostic/detection or therapeutic agent conjugated to the fijsion protein or fragment thereof Considered herein is a method of treatii a malignancy in a subject, comprisii the step of administerit to said subject a therapeutically effective amount of a naked and/or conjugated anti-AFP antibody, fiision protein, or fragment tiiereof of the present invention, formulated in a pharmaceutically acceptable vehicle, either alone or in combination with other therapeutic and/or diagnostic agents. PrefCTably, the method a method of treating a malignancy in a subject, comprising the step of administering to said subject a therapeutically effective amount of a immimoconjugate or fragment thereof the present invention, formulated in a pharmaceutically acceptable vehicle. Similarly, a method of diagnosing/detecting a malignancy in a subject, comprising the step of administering to said subject a diagnostically effective amount of a naked or conjugated anti-AFP antibody, fusion protein, or fragment thereof of the present invention, formulated in a pharmaceutically acceptable vehicle. Another embodiment is a method of treating or diagnosing/detecting a malignancy in a subject, comprising (i) administering to a subject in need thereof the anti-AFP antibody or fragments thereof of the present invention; (ii) waitmg a sufficient amount of time for a desired amount of the non-binding prot to cledr the subject's bloodstream; and (iii) administering to said subject a carrier molecuk consing a diagnostic agent, a therapeutic agent, or a combination thereof, that bmds to a bmding site of said antibody. Another embodiment of the present invention is a DNA sequence and a vector coirrising a DNA sequence, and a host cell comprising a DNA sequence, tbat comprises a nucleic acid encoding an anti-AFP MAb or fragment thereof selected from the groiq) consisting (a) an anti-AFP MAb or fragment tiiereof of the prreent invention; (b) an antibody ftision protein or fr-ment tiiereof comprising at least two of said MAbs or fragments Uiereof; (c) an antibody fiision protein or fragment thereof comprising at least one first AFP MAb or fragment thereof comprising said MAb or fragment thereof of any one of the antibothes of the present invention arui at least one second MAb or fragment thereof, other than (he anti-AFP MAb or fragment thereof described in the present invention; and (d) an antibody frision protein or fragment thereof comprising at least one first MAb or fragment tlreof comprising said MAb or fragment thereof of any one of the antibothes of the present invention and at least one second MAb or fragment thereof, other than the anti-AFP MAb or fragment thereof of any one of the antibothes of the present invention, wherein said second MAb is selected from tiie group consisting of CEA, EGP-1, EGP-2 (e.g., 17-1 A), MUC-1, MUC-2, MUC-3, MUC'4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigens, ferritin, acidic isoferritin, Ga 733, or a combination thereof Other suitable second antibothes include those that bind tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothelium growth fector (VEGF), placental growth factor (PIGF), ED-B fibronectm, and against ofiier vascular growth factors. A method of delivering a diagnostic/detection or therapeutic agent, or a combinatioii thereof to a target comprisii (i) providing a composition comprisimg an immunoconjugate tlrat comprises the antibody, fusion protein, or frjpient thereof of any one of the antibothes, fusion protems, or fiBgmaats thereof of the present invention and (ii) administering to a subject in need thereof said composition, is also described. Preferably, the diagnostic/detection agent comprises at least one photoactive diagnostic agent, such as a chromagen or dye, a contrast agent, such as a paramagnetic ion, an ultrasound-enhancing agent or a radiopaque compound used in X-rays or computed tomography, such as an iodine compound, barium compound gallium compound or thalhum compound. In one embodiment, the ultrasound enhancing agent is a liposome that comprises a humanized Immu31 or fragment thereof and optionally, the liposome is gas-filled. In anotiier embodiment, the diagnostic/detection agent preferably is a radionuclide with an energy between 20 and 2,000 keV, such as a gamma-, beta- or a positron-emittir isotope. Still jKcfened, the radionuclide is selected &om the group consisting of F-18, Mn-51, lvbi'52m, Fe-52, Co-S5, Cu-62, Cu-64, Ga-68, As-72, Br-75, Br-76, Rb-82m, Sr-83, Y-86, Zr-89, Tc-94m,In-110,1-120,1-124, Cr-51, Co-57, Co-58, Fe-59, Cu-67, Ga-67, Se-75, Ru-97, Tc-99m, In-n 1, In-U4m, I-I23.1-125,1-131, Yb-I69, Hg-197, and Tl-201. Also preferred, the radiopaque compound is selected fiom the group consisting of barium, diatrizoate, ethiodized oil, gallium citrate, iocarmic acid, iocetamic acid, iodamide, iodipamide, iodoxamic acid, iogulamide, iohexol, iopamidol, iopanoic acid, ioprocemic acid, ioscfamtc acid, ioseric acid, tosulamide megliunine, iosemedc acid, iotasul, iotetric acid, iothalamic acid, iotroxic id, ioxlic acid, ioxotrizoic acid, ipodate, meglumine, metrizamide, metrizoate, propyliodone, and thallous chloride. Similarly, in the method of delivering a diagnostic/diction or therapeutic agent, or a combination thereof, to a target, the therapeutic agent is preferably selected from the group consisting of a radionuclide, an immunomodulator, a hormone, a hormone antagonist, an enzyme, an enzyme inhibitor, a photoactive therapeutic agent, a cytotoxic agent, such as a drug or toxin (including a plant, microbial and animal toxin, and a synthetic variation thereof), and a combination thereof Preferably, the drug is selected from the gro'i consisting of antimitotic, alkylating, antimetabolite, antiangiogenic, apoptotic, anthracyclines, alkaloid, COX-2-inhibitor and antibiotic agents, and combinations thereol nitrogen mustards, ethylenimine derivatives, alkyi sulfonates, nitrosoureas, triazenes, folic acid analogs, anthracyclines, taxanes, COX-2 inhibitors, pyrimidine analogs, purine analogs, antibiotics, enzymes, enzyme inhibitors, epipodophyllotoxins, platinum coordination complexes, vinca alkaloids, substituted ureas, metiiyl hydrazine derivatives, adrenocortical suppressants, hormones, hormone antagonists, endostatin, taxols, camptothecins, doxorubicins and their analogs, and a combination thereof. Also preferred, the toxin is selected from the group consisting of ricin, abrin, alpha toxin, saporin, ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtherin toxin, Pseudomonas exotoxin, and Pseudomonas endotoxin. Also considered herein is a method of delivering a diagnostic/detection agent, a thempeutic agent, or a combination thereof to a taiet, comprising: (i) administering to a subject a multivalent, multlspecific antibody or fragment thereof of the present invention; (ii) waiting a sufiicient amount of time for an amount of the non-binding protein to clear &e subject's blood stream; and (iii) administering to said subject a carrier molecule comprising a diagnostic/detection agent, a therapeutic agent, or a combination thereof, that binds to a binding site of said antibody. Preferably, the multivalent, multispecific antibody or fragment thereof comprises one or more antigen binding sites having afOnity toward an AFP target antigen and one or more hapten binding sites having an affinity towards hapten molecules. Preferably, the carrier molecule bmds to more than one bindmg site of the antibody. Also preferred, the diagnostic/detection agent or said therapeutic agent is selected from the group comprising isotopes, dyes, chromagens, contrast agents, drugs, toxins, cytokines, enzymes, enzyme inhibitors, hormones, hormone antagonists, growth factors, radionuchdes, and metals. Contemplated herein is a method of treating a malignancy in a subject comprising administering to said subject a therapeutically effective amount of (i) an antibody or fragment thereof or (ii) an antibody fusion protein or fragment thereof, wiierein the antibody or fragment thereof comprises at least two MAbs or frraents tiiereot at least one of which is any of the anti-AFP MAb or fragment thereof of the present invention, and the fusion protein or fragment thereof comprises at least one AFP binding site, fonnulated in a phannaceutically suitable excifaent. In a preferred embodiment, at least one of the Mabs or fragmente thereof is a naked Nfeb or fragment thereof. In another embodiment, tbe fiision protein comprises a second binding site that is reactive with a tumor marker substance other than AFP. Also contemplated is that fee anti-AFP antibody or fragmait feereof, or anti-AFP fusion protein or fragment thereof is administered before, concurrently, or after at least one therapeutic or diagnostic/detection ent Another embo(&nent is a method of treating a malignancy in a subject comprisii administerii to said subject a therapeutirally efective amount of an antibody or fragment thereof comprising at least two MAbs or fragments feereof, wherein fee MAbs are selected from any one of fee anti-AFP antibothes described herein, and formulated in a pharmaceutically suitable excipient In a preferred embodiment, at least one of fee Mabs or fragments thereof is a naked Mab or fragment thereof. Also cantemplated is that the anti-AFP antibody or fragment thereof, or anti-AFP ftision protein or fragment feereof, is administered before, concurrently, or after at least one feerapeutic and/or diagnostic/detection ent In fee mefeod of treatment desribed herein, fee anti-AFP antibody is selected from fee group consisting of a subhuman primate anti-AFP antibody, murine monoclonal anti-AFP antibody, chimeric anti-AFP antibody, human anti-AFP antibody, and humanized anti- AFP antibody. Preferably, the chimeric, himian and hiraianized anti-AFP antibody constant and hiie rons conjiise constant and hinge regions of a human IgOl. Also in fee mefeods described herein, the anti-AFP antibody or fragment feereof or fiision protein or frment feereof is administered before, in conjunction wife, or after a second conjugated antibody reactive wife a second tumor marker expressed by said malignancy is administered to said subject The present invention also describes a mefeod of disposing or detecting a malignancy in a subject comprising administering to said subject a diagnostically effective amount of a diagnostic/detecting conjugate comprising a anti-AFP MAb or fragment feereof or a friston protein or fragment feereof of as described in the present invention, wherein fee anti-AFP MAb or fragment thereof, or fiision protein or fragment thereof, is bound to at least one diagnostic/detection agent, fonnulated in a phannaceuticaily suitable excipient Another embodiment of the present inventioa is a method of treating acancer cell in a subject comprising (i) administering to said subject a therapeutically effective amount of a composition comprising a naked or conjugatel anti-AFP MAb or fragment thereof or a naked or conjugated antibody fusion protein or fragment thereof, as described in the present invention, (ii) formulating said anti-AFP MAb or fragment thereof or antibody fiision protein or fragment thereof in a phannaceuticaily suitable excipient Preferably, the anti-AFP antibody, fijsion protein, or fragment thereof is an Immu31 antibody, frision protem, or fi-ment thereof. Optionally, the composition may fiather comprise a second naked or conjugated antibody or fragment thereof, or naked or conjugated antibody fusion protein or fragment thereof, that may or be an anti-AFP antibody, fusion protein or fragment thereof or may bind a second tumor raaAer expressed by the malignancy. Also considered is that the anti-AFP antibody, antibody fiision protein, or fragment thereof, is adrainistei«d before, in conjunction with, or after a second antibody, fusion protein, or fragment thereof is administered to said subject The anti-AFP antibody may also be administered before, concuirently or after a therapeutic or dinostic/detection agent The present invention also describes a method of dinosing or detecting a malignancy in a subject comprising (i) performing an in vitro diagnosis assay on a specimen from the subject with a composition comprising an anti-AFP MAb or fragment thereof or an antibody fusion protein or fragment thereof described herein. Preferably the malipiancy is a carcinoma expressing AFP, such as a hepatocellular carcinoma, a hepatoblastoma or a gemi cell tumor. Also preferred, the in vitro diagnosis assay is selected fixDm the group consisting of immunoassays, RT-PCR and immunohistochemistry. If the diagnostic assay is RT-PCR or immunoassays, the specimen is preferably body fluid or a tissue or cell population. If the diagnostic assay is immunohistochemistry or immunocytochemistiy, the specimen is preferably a cell aliquot or a tissue. In any of the methods of the present invention, the subject is preferably a maimnal, such as a human or domestic pet. Another embodiment of the present invention is a method of treating or identifying diseased tissues in a subject, comprising: (A) administering to said subject a bi-specific antibody or antibody fragment having at least one arm tiiat specifically biads a diseased tissue-associated marker and at least one other aim thai. speciiicaUy binds a targetable conjugate, wherein said diseased tissue-associated marfcer is AFP; (B) optionally, administering to said subject a clearing composition, and allowing said composition to clear non-localized antibothes or antibody fragments from circulation; (C) administering to said subject a first targetable conjugate which comprises a carrier portion which comprises or bears at let one q)itope recognizle by said at least one other arm of said bi-specific antibody or antibody fragment, and one or more conjugated tiierapeutic or diagnostic ents; and (D) when said therapeutic agent is an enzyme, further administering to said subject (i) a prodrug, vsen said enzyme is capable of converting said prodrug to a drug at the target site; or (ii) a drug wiiich is capable of being detoxified in said subject to form an intermediate of lower toxicity, when said enzyme is capable of reconverting said detoxified intermediate to a toxic form, and, tiierefore, of increasing the toxicity of said drug at the target site, or (iii) a prodrug which is activated in said subject through natural processes and is subject to detoxification by conversion to an intermediate of lower toxicity, wlien said enzyme is capable of reconverting said detoxified intermediate to a toxic form, and, therefore, of increasing the toxicity of sd drug at the target site, or (iv) a second targetable conjugate wWch comprises a carrier portion which comprises or bears at least one epitope recognizable by said at least one other arm of said bi-specific antibody or antibody fragment, and a prodrug, vrfien said enzyme is capable of convertii said prodrug to a drug at the target site. Preferably, at least one arm that specifically binds a tergeted tissue is a human, chimeric or humartized lmmu31 antibody or a fragment of a human, chimeric or hamanizedlmmu31 antibody. Also preferred, the targetable conjugate comprises at least two HSG haptens. Preferably, the targeted tissue is a tumor and more preferably, the tumor produces or is associated with alpha-fetoprotein (AFP). Also preferred, the lmmu31 antibody or fiagment thereof comprises the Fv of MAb Immu31. This method may further comprise, v/hen said first targetable conjugate comprises a prodrug, administering a second targetable conjugate which comprises a carrier portion which comprises or bears at least one epitope recognizable by said at least one other arm of said bi-specific antibody or antibody fragment, and an enzyme capable of converting said prodmg to a drug or of reconverting a detoxified intermediate of said drug to a toxic fonn Preferably, the prodrug is selected from the group consisting of epirubicin glucuronide, CPT-11, etoposide glucuronide, daunomicin glucuronide and doxombicin glucuronide. Also preferred, the targetable conjugate comprises one or more radioactive isotopes usefiil for killing diseased tissue. Tlie targetable conjugate may comprise one or more agents for photodynamic thery, such as a photosensitizer. In a preferred embodiment, the photosensitizer is selected from the group consisting of benzoporphyrin monoacid ring A (BPD-MA), tin etiopurpittin (SnET2), sulfonated aluminum phthalocyanine (AlSPc) and lutetium texiqjhyrin (Lutex). Considered herein is a method for detecting or treatii tumors expressing AFP in a mammal, comprisiag; (A) administering an effective amomit of a bispecific antibody or antibody fragment comprising at least one arm that specifically binds a targeted tissue and at least one other arm that specifically binds a targetable conjugate, wherein said one arm that specifically binds a targeted tissue is an Immu31 antibody or figment thereof; and (B) administering a targetable conjugate selected fix>m the groiq> consisting of (i) DOTA-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-NH2;(u) DOTA-Phe-Lys(HSG)-Tyr-Lys(HSG>NH2; (iii) Ac-Lys(HSG)D-Tyr-Lys(HSG)-Lys(Tscg-Cys>NH2: Preferably, the method further comprises administering to the subject a clearing composition, and allowing said composition to increase clearance of non-localized antibothes or antibody fragments fiom circulation. Also contsnplated herein is a kit useful for treating or identifying diseased tissura in a subject comprising: (A) a bi-specific antibody or antibody fragment having at least one ann that specifically binds a targeted tissue and at least one olher arm that specifically binds a targetable conjugate, \erein said one arm tiiat specifically binds a targeted tissue is an lmmu31 antibody or fragment thereof; (B) a first taietable conjugate vch comprises a carrier portion vch comprises or bears at least one epitope recognizable by said at least one other arm of said bi-specific antibody or antibody fiagment, and one or more conjugated therqwutic or diagnostic agents; and (C) optionally, a clearing composition useful for clearing non-localized antibothes and antibody fragments; and (D) optionally, when said therapeutic agent conjugated to said first targetable conjugate is an enzyme, (i) a prodrug, when said enzyme is enable of converting said prodrug to a drug at the target site; or (ii) a drug which is capable of being detoxified in said subject to form an intennediate of lower toxicity, when said enzyme is capable of reconverting said detoxified intermediate to a toxic form, and, therefore, of increasing the toxicity of said drug at the target site, or (iii) a prodrug which is activated in said subject through natural processes and is subject to detoxification by conversion to an intermediate of lower toxicity, wiien said enzyme is capable of reconverting said detoxified intermediate to a toxic form, and, therefore, of increasing the toxicity of said drug at the target site, or (iv) a second targetable conjugate wch conwises a carrier portion which comprises or bears at least one epitope recognizable by said at least one other aim of said bi-specific antibody or antibody (ragment, and a prodrug, when said enzyme is capable of converting said prodrug to a drug at the target site. Preferably, the targetable conjiate is selected from the group consisting of: Also described in the present invention is a method of screening for a targetable conjugate comprising: (A) contacting said targetable construct with a bi-specific antibody or antibody fragment having at least one arm that specifically binds a marker associated with a targeted tissue, wherein said maricer is AFP, and at least one other arm that specifically binds said targetable conjugate to give a mixture; and (B) optionally incubating the mixture; and (C) analyzing the mixture. Another embodiment is a method for imaging malignant tissue or cells in a mammal expressing AFP, comprising: (A) administering an efiFective amount of a bispecific antibody or antibody fragment comprising at least one arm that specifically binds a marker associated with a targeted tissue and at least one other arm that specifically binds a targetable conjugate, wherein said marker is AFP; and (B) administering a targetable conjugate selected fix)m the ©lotq) coMisting of The invention also contemplates a method of intraoperatively identifying/disclosing diseased tissues expressing AFP, in a subject, comprising: (A) administering an effective amount of a bispecific antibody or antibody ftagment comprising at least one arm that specifically binds AFP and at least one other arm that specifically binds a targetable conjugate, wherein said one arm that specifically binds Also described herein is a method for the endoscopic identification of diseased tissues expressing AFP, in a subject, comprising: (A) administering an effective amount of a bispecific antibody or antibody fragment comprising at least one arm that specifically binds AFP and at least one other arm that specifically binds a targetable * conjugate wherein said one arm that specifically binds a targeted tissue is a Immu31 antibody or fragment thereof; and (B) administering a targetable conjugate selected from the ©roup consisting of (i)D0TA-Phe-Lys(HSG)-D-Tyr-Lys(HSG>NH2; fii) D0TA-Phe-Lys(HSG)-Tyr-Lys(HSG)-NH2; Another embodiment is a method for the intravascular identification of diseased tissu) expressing AFP, in a subject, comprising: (A) administering an effective amount of a bispecific antibody or antibody ftagment comprising at least one aim that specificaUy binds AFP and at least one other arm that specificaUy binds a targetable conjugate wherein said one ami tiiat specifically binds a targeted tissue is a Immii31 antibody or firagmeait thereof; and (B) administering a targetable coajiate selected fixjm the group consisting of (i)D0TA-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-NH2; Cu)DOTA-Phe-Lys(HSG)-Tyr-Lys(HSG)-NH2; (iii)Ac-Lys(HSG)D-Tyr-Lys(HSG)-Lys(TscB-Cys)->fH2; Another embodiment is a method of detecting lesions, preferably durii an endoscopic, laparoscopic, intravascular catheter, or surgical procedure, wterein the method conrises: (A) injecting a subject who is to undergo such a procedure with a bispecific antibody F(ab)2 or F(ab% fragment, wtherein the bispecific antibody or fragment has a first antibody binding site wliich specifically binds to a AFP antigen, and has a second antibody landing site vAaiAi specifically binds to a hJtai, and peraiitting the antibody fragment to accrete at target sites; (B) optionally clearing non-targeted antibody fragnients using a galactosylated anti-idiotype clearii agent if the bispecific figment is not largely cleared from circulation within about 24 hours of injection, and injecting a bivalent labeled hten, vAndi quickly localizes at the taiget site and clears through the kidneys; (C) detecting the presence of the hapten by close-raie detection of elevated levels of accreted label at the target sites with detection means, within 48 hours of the first injection, and conducting said procedure, wherein said detection is performed without the use of a contrast agent or subtraction agent In a preferred embodiment, the hapten is labeled with a diagnostic/detection radioisotope, a MRI image-enhancing agent or a fluorescent label. Also considered is a method for close-range lesion detection, preferably during an operative, intravascular, laparoscopic, or endoscopic procedure, wherein the method comprises: (A) injecting a subject to such a procedure parenterally with an effective amount of an ImmuSl immunoconjugate or fragment thereof, (B) conducting the procedure wilhin 48 hours of the injection; (C) scanning the accessed interior of the subject at close range with a detection means for detecting the presence of said labeled antibody or fragment thereof; and (D) locating the sites of accretion of said labeled antibody or fragment thereof by detecting elevated levels of said labeled antibody or fragment thereof at such sites with the detection means. Preferably, the Immu31 immunoconjiate or fragment thereof comprises a radioisotope that emits at an energy of 20-1,000 keV. Also preferred, the radioisotope is selected from the group consisting of technetium-99m, iodine-125, iodine-131, iodine-123, indium-111, fluorine-18, galliimi 68 and gallium-67. In another embodiment, ImmuS 1 immunoconjugate or fragment thereof comprises a non-isotopic agent, such as a photoactive agent. BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows the cloned VH and VK gene sequences of the murine Immu31 by RT-PCR and the deduced amino acid sequences. Underlined at 5'-ends are the PCR primer sequences used in cloning. Only the sequences of variable regions are shown, therefore, the 3'-end PCR primer sequences are not shown. Figure lA shows the DNA and amino acid sequences of the ImmuBlVH. Figure IB shows the DNA and amino acid sequences of the Inunu31VK. Amino acid sequences encoded by the corresponding DNA sequences are given as one letter codes below the nucleotide sequence. Numbering ofthe nucleotide sequence is on the right side. The amino acid residues in the CDR regions are shown in bold and underlined. Rabat's Ig molecule numbering is used for amino acid residues as shown by ttie numberii above the amino acid residues. The residues numbered by a letter following digits indicate the insertion residues defined by Kabat numbering scheme. The insertion residues numbered with a letter only have the same preceeding digits as the previous one. For example, residues 82,82A, 82B and 82C in Figure 1A are indicated as 82, A, B, and C, respectively. Figure 2 shows the DNA and amino acid sequences of the chimeric Immu31 (clmmu31) heavy and light chain variable regions expressed in Sp2/0 cells. Figure 2A shows the DNA and amino acid sequences of the clirunu31 VH- Figure 2B shbws the DNA and amino acid sequences of the clmmuSlVic Amino acid sequences encoded by the corresponding DNA sequences are given as one letter codes. The amino acid residues in the CDR regions are shown in bold and underlined. Numbering of the nucleotide sequence is on the right side. The numbering of amino acids is same as that in Figure 1. Tlie restriction sites used for construction of the clmmu31 are boxed and indicated. Figure 3 shows the results of a competitive cell surface-binding assay to compare the binding athnity of clmmu31 with that of murine Immu31. Varying concentrations of clmmu31 (triangle line) or mlmmu31 (diamond line) were mixed with a constant amount of biotinylated murine ImmuSl and incubated for 1 bin the wells of 96-weIl ELISA plate precoated with AFP. After washing, HRP-conjugated streptavidin was added and incubated for 1 h at room temperature. The amount of HRP-conjugated streptavidin bound to the AFP-bound biotinylated IimnuJ 1 was revealed by reading OD490 after the addition of a substrate solution containing 4 mM ortho-phenylenediamine dihydrochloride and 0.04% H2O2. The results showed that clmmu31 and the murine lmmu31 competed equally well for the binding of radiolabeled hnmu31 to AFP, confirming the cloned V genes are authentic. Figure 4 shows the aligimient of the amino acid sequences of light and heavy chain variable regions of the human antibothes, mouse ImmuSI and hlmmu31. Figure 4A shows the aligrunentofthe VH sequences of EU,NEWM, Immu31, and hlmmu31, and Figure 4B shows the VK sequence aiigimient of REI, Immu31 and hlmmu31. Dots indicate the residues in Immu31 and hlrrmiu31 that are identical to the corresponding residues in the human antibothes. Dashes indicate the gaps introduced into the sequences to facilitate the aligimient. Boxed rions re|sesent the CDR regions. Both N- and C-tenninal residues (underlined) of hlmmu31 are fixed by the staging vectors used. Kabat's Ig molecule numbering scheme is used as in Fig. 1A and Fig. IB. Figure 4C shows the sequence alignment of hlmmu31 VK and the vatiants, hlmmii31 VKT69 and hlmmu3 1VKT39. Dots indicate the residues in hImmu31VKT69 andhImmu31VKT39 that are identical to the corresponding residues ofhlmmuSlVK. Figure 5 shows the DNA and amino acid sequences of the humanized hnmu31 (hhnmuS 1) heavy and light chain variable regions expressed in Sp2/0 cells. Figure 5A shows the DNA and amino acid sequences of the hImmuSlVH and Figure SB shoMra the DNA and amino acid sequences of the hlmmuSl VK. Amino acid sequences encoded by the corresponding DNA sequences are given as one letter codes. The amino acid residues in the CDR regions arc shown in bold and underlined, Kabat's Ig molecule nimibering scheme is used for amino acid residues as in Fig. 1A and Fig. IB. Figure 6 shows the results of competitive cell surface binding assays to compare the binding afSnity of hlmmu31 and two variants, hImm31T39 and hIinmu3IT69, with that of murine and chimeric Immu31. Varying concentrations of a competing Ab, {hJmmu3 J, hlmm31T39, hlnimu31T69, clmmu31, or (murine) Immu31) was mixed with a constant amount of biotinylated murine Inimu31 and incubated for 1 h in the wells of 96-weIl ELISA plate precoated with AFP, After washing, HRP-conjugated streptavidin was added and incubated for 1 h at room temperature. The amount of HRP-conjugated streptavidin bound to tiie AFP-bound biotinylated Immu31 was revealed by readmg OD490 after the addition of a substrate solution containing 4 mM ortho-phenylenediamine dihydrochloride and 0.04% H2O2. Chart A compares the binding affinity of hlmmu31 (triangle) and hImmu31T69 (cross) with clmmu31 (square) and Immu31 (diamond). The results showed that hlmmu31, clmmu31 and Immu31 competed with biotin-Immu31 equally well for the binding to AFP, indicating the binding specificity and affinity of MAb Immu31 are preserved in the humanized Immu31. In addition, the binding affinity of hImmu31T69 to AFP was shown to be comparable to other Immu31 Abs. Chart B compares hImmu3IT39 (triangle) with hlmmu31 (square) and Inunu31 (diamond). The binding affinity of hlnimu31T39 was reduced significantly, indicating the importance of the charged residue 39K in Ag-bindii. Figure 7 shows the results of competitive cell surfece binding assays to compare the bmding affinity of hlmmu31 expression using pdHL2 vector with that chimeric Immu31. DETAILED DESCRIPTION OF THE DSTVENTION 1. Overview The present invention provides murine, humanized, chimeric and human anti-alpha-fetoprotein (AFP) antibothes, ilision proteins, or fragments thereof useful for treatment and/or diagnosis of manunalian subjects, as an immunoconjugdte or in combination with, but unconjugated to, other therapeutic and/or diagnostic agents. In a preferred embodiment, the anti-AFF antibody is an Immu31 antibody. The Immu31 antibothes and frments thereof bind the alpha-fetoprotein antigen. As used herein, the phrase "Immu3I" antibody or fi-agraents means any antibody or fragment that binds the same epitope on the AFP antigen as an antibody or antibody fragment comprising CDRl of a heavy chain variable region that comprises an amino acid sequence of SYVIH, CDR2 of a heavy chain variable regjon that comprises an amino acid sequence of YIHPYNGGTK.YNEKFKG, CDR3 of a heavy cham variable region that comprises an amino acid sequence of SGGGDPFAY, and CDRl of a light chain variable region that comprises an amino acid sequence of KASQDINKYIG, CDR2 of a light chain variable region that comprises an amino acid sequence of YTSALLP, and CDR3 of a light chain variable region that comprises an amino acid sequence of LQYDDLWT. The Immu31 antibothes, ftision proteins, and fragments thereof of the present invention may also be administered with another conjugated or unconjugated Immu31 antibody, fiision protein, or fragment therof, or a conjugated or unconjugated non-Immu31 antibody, fijsion protein, or fragment thereof. The chimeric or humanized anti-AFF MAbs and fragments thereof of the present invention contain specific murine CDRs or a combination of murine CDRs fmm more than one murine or chimeric anti-AFF MAb. Preferably, the chimeric and humanized anti-AFP antibothes of the present invention contain CDRs from a muring ImmuSl antibody. ThelmmiOl Mabsand fragments thereofofthe present invention are murine, humanized, chimeric or fUlIy human Mabs. The chimeric and humanized antibothes contain the amino acid sequence of the CDRs of a murine hninu31 (mlmmu31) MAb and the light and heavy chain constant regions of a human antibody. In a preferred embodiment, the humanized Immn31 MAb or fragment thereof of the present invention comprises the CDRs of a murine Immu31 MAb and the frameworii (FR) regions of the light and heavy chain variable regions of a human antibody and the light and heavy chain constant regions of a human antibody. Preferably, the CDRs of the light diain variable region of the humanized himm31 MAb comprises CDRl comprising amino acids KASQDINKYIG; CDR2 comprising amino acids YTSALLP; and CDR3 comprising amino acids LQYDDLWT; and the CDRs of the heavy chain variable region of the himiu31 MAb conqirises CDR1 comprising ammo acids SYVIH; CDR2 comprising amino acids YMPYNGGTKYNEKFKG and CDR3 comprising ammo acids SGGGDPFAY. In another embodiment, the humanized Immu31 MAb or fragment thereof may fiirther contain in the FRs of the light and heavy chain variable regions of the hlmmu31 antibody, at least one amino acid from the corresponding FRs of the mvttine MAb. Specifically, the humanized Immii31 MAb or fragment thereof contains at least one amino acid residue 5,27,28,30,46,48,66, 67 and 94 of the murine heavy chain variable region of Fig. 5A, designated as hImmu31VH and of at least one amino acid residue 4,39,48,49, 58,69,100 and 107 of the murine Kght chain variable ron Fig. 5B, designated hlmmu31 Vk. One or more of the murine amino acid sequHices can be maintained in the human FR regions of the light and heavy variable chains if necessaiy to maintain proper binding or to enhance binding to AFP. More preferably the humanized Inimu31 MAb or fragment thereof of the present invention comprises the hlmmu31 VH of Figure 5A and the hlmmu31 VK of Figure SB. In a related vein, chimeric Immu31 (clmmu31) MAb or fragment thereof of the present invention comprises the CDRs of a murine Immu31 MAb and the FR regions of the light and heavy chain variable regions of the murine Immu31 MAb. In other words, the clmniu31 antibody comprises the Fvs of the parental murine (i.e., mlmmuBI) MAb, and the light and heavy chain constant regions of a human antibody, wherein the CDRs of the light chain variable region of the chimeric InuuuSl MAb comprise CDRl comprising amino acids KASQDINKYIG; CDR2 comprising amino acids YTSALLP; and CDRS comprising amino acids LQYDDLWT; and the CDRs of the heavy chain variable region of the chimeric Immu31 MAb comprise CDRl comprMng amino acids SYVIH; CDR2 comprising amino acids YIHPYNGGTKYNEKFKG and CDR3 comprismg SGGGDPFAY. More preferably the chimeric hnmu31 MAb or fiagment thereof conrises the complementarity-determining regions (CDRs) of a murine Immu31 MAb and the framewoik (FR) regions of the light and heavy chain variable regions of the murine Immvi31 MAb and the light and heavy diaio content regions of a human antibody, wherein tbs CDRs and FRs of the heavy and light chain variable region of the chimaic Immu31 MAb comprise the sequence shown in Figs. 2A and 2B, respectively, designated cImmu31VH and chnmuSlVic The present invention also contemplates antibody fusion proteins or fragments thereof comprising at least two anti-AFP MAbs or fragments thereof. Preferably, the anti-APP antibothes and fragments therof are the bnmu31 antibothes and frments thereof of the present invention. Also preferred, the antibody fiision proteins of the present invention are composed of one anti-AFP MAb and one or more of the second MAbs to provide specificity to different antigens, and are described in more detail below. Likewise, the antibody fusion protein of the present mvention can be used in combmation with yet another antibody. For example, the antibody frision protein can be used in combination therapy with another antibody, which can be administered before, after or concurrentiy with the fusion protein, and is reactive with an antgen selected from the group consisting of CEA, EGP-1, EGP-2 (e.g., 17-lA), MUC-1, MUC-2, MUC-3, MUC-4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigenstenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothelium growth frictor (VEGF), placental owth fktor (PIGF), ED-B fibronectin, and other vascular grovrth factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof. In another preferred embodiment, the anti-AFP antibody is an Immu31 antibody and the antibody fbsion protein or firngment thereof of the present invention is also intended to encompass an antibody fusion protein or fragment thereof conqirising at least one first Immu31 MAb or frment thereof as described above and at least one second non-Immu31 MAb or fiagment thereof. Preferably, the non-Immu31 antibody OT fragment thereof is a carcinoma associated antibody. More preferably the carcinoma associated MAb is aMAb reactive with CEA, EGP-1, EGP-2 (e.g., 17-lA), MUC-1, MUC-2, MUC-3, MUC-4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigenstenascin, an oncogene, an oncogene product, IL-6, lGF-1, IGFR-1, tumor angjogenesis antigens, such as vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectin, and other vascular growth factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof, and even an anti-AFP MAb that is different from the ImmuS 1 MAb described herein. The humanized, chimeric and human Immu31 antibody may possess enhanced affinity binding with the epitope as a result of CDR mutation and manipulation of the CDR and other sequences in the variable region to obtain a superior therapeutic agent for the treatment of hepatocellular carcinoma, hepatoblastoma, germ ceil tumors, and other a-fetoprotein (AFP) producing tumors. Modification to the binding specificity, affinity or avidity of an antibody is known and described in WO 98/44001, as affinity maturation, and tMs application summarizes methods of modification and is incorporated in its entirety by reference. It may also be desirable to modify the antibothes of the present invention to improve effector function, e.g., so as to ehance antigen-dependent cell-mediated cytotoxicity (ADCC) and/or complement dependent cytotoxicity (CDC) of tiie antagonist. One or more amino acid substitutions or the introduction of cysteine in the Fc region may be made, thereby improving intemalization capability and/or increased complement-mediated ceil killing and ADCC. See Caron et al., J. Ex. Med. 176:1191-1195 (1991)andShopes,fi.y./miww«o/. 148:2918-2022(1992), incorporated herein by reference in their entirety. An antibody fiision protein may be prepared that has dual Fc regions with bodi enhanced complement lysis and ADCC capabilites. Another embodiment of the present invention is a DNA sequence comprising a nucleic acid encoding a MAb or fiagment thereof selected fiom the group consisting (a) an Immu31 MAb or fragment thereof as described herein, (b) an antibody fusion protein or fragment thereof comprisii at least of the hnmu31 MAbs or fiagmentsthereofofthepresait invention, (c) an antibody fusion protein or fragment thereof comprisii at least one first MAb or fragment thereof comprising an ImmuS 1 MAb or fragment thereof as described herein and at least one second MAb or fi:ment thereof other iban the hnmu31 MAb or fragment thereof described herein, and (d) an antibody fusion protein or fragment thereof comprising at least one first MAb or fragment thereof conrising the Immu31 MAb or fragment thereof and at least one second MAb or fragment thereof, wtherein the second MAb is a carcinoma associated MAb reactive with CEA, EGP-1, EGP-2 (e.g., 17-1 A), MUC-1, MUC-2, MUC-3, MUC-4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigens, tenascin, an oncogene, an oncogene product, IL-6,1GF-1,1GFR-1, tumor angiogenesis antigens, such as vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectin, and other vascular growth factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof hi a related vein, expression vectors comprising the DNA sequences are also considered herein. In the case of vectors for use in preparing tiie humanized, chimeric and human hnmu31 MAIB or antibody fusion proteins thereof or fragments thereof these vectors contain the coding sequences for the light and heavy chain constant rons and the hinge region of the human immunoglobulin, as well as the secretion signal peptide. These vectors addtionally contain, where requried, promoter/enhancer elements to initiate the Ig graie expression in the selected host cell, and a drug-resistant marker for selection of transfected cells. Vectors that are particularly useful in the present invention are DHFR (sudi as pdHl) or GS-vector, particularly vib&a Ms&i to express a chimeric. humanizjed or human antibody, such as an IgG, where the vector codes for the heavy and light chain constant regions and hinge leon of IgGl. More preferably, the Ut and heavy chain constant regiom and hire region are from a human EU myelonm immunoglobulin, where optionally at least one of the amino acid residues in the allotype positions is chained to that found in a different IgGl allotype, and wiierein optionally amino acid 1253 of fee heavy chain of EU (based on the EU numbering system) may be replaced with alanine. See Edelman etal, Proc. Natl Acad Sci USA 63: 78-85 (1969), incorporated herein in its entirety by reference. Host cells containing the DNA sequences encoding the Immu31 MAbs or fragnents thereof or antibody fiKion proteins or frEments tiioBof of tiw present invention or host cells containing the vectors that contain these DNA sequences are encompassed by the present invention. Particularly usefiil host cells are mammalian cells, and more specifically, myeloma cell lines, such as Sp2/0, YB2/0, NSO, and CHO, such as DG-44, as discussed in more detail below. Also useful for producing monoclonal antibothes and other fiision proteins is the PER.C6 human cell line. Also encompassed by the present invention is the method of expressii a Imniu31 MAb or fragment thereof or a Inimu31 fiision protein or fianent thereof comprising: (a) transfectir a mammalian cell with aDNA sequence of encoding a Immu31 MAb or fragment thereof or an antibody fiision protein or fragments thereof, and (b) culturing the cell transfected with the DNA sequence that secretes tiie Immu31 or fragment ttiereof or Immu31 antibody frision protein or fragment thereof Known techniques may be used that include a selection marker on the vector so that host cells that express the MAbs and the mariter can be easily selected. The present invention also encompasses liver cell targeting diagnostic/detection or therapeutic immunoconjugates comprising an anti-AFP MAb or fiment thaeof or an anti-AFP fiision protein or fi-agraent thereof, that bind to the AFP expressing cell and is bound to at least one diagnostic/detection and/or at least one therjeutic ent In a preferred embodiment, the diaostic/detection immunoconjugate comprises an Inunu31 MAb or fiagjnent thereof or an antibody fiision protein or fragment thereof, and at least one diagnostic/detection agent. Examples of dinostic/detection agents include diverse labels, radionuclides, chelators, dyes, fluorescent compounds, chromagens, and other maricer moieties. Radionuclides usefiil for positron emission tomography include, but are not limited to: F-18, Mn-51, Mn-52m, Fe-52, Co-55, Cu-62, Cu-64, Ga-68, As-72, Br-75, Br-76, Rb-82m, Sr-83, Y-86, Zr-89, Tc-94m, In-liO, 1-120, and 1-124. Total decay energies of useful positron-emitting radionuclides are preferably Also preferred, the therjeutic mmunoconjugate of the present invention comprises an Immu31 antibody or fragment thereof, or an Immu31 fusion protein or fragment thereof, and at least one therapeutic agent Examples of therapeutic agents include a radioactive label, an immunomodulator, a homione, a photoactive therapeutic agent, a cytotoxic agent, wdiich may be a drug or a toxin, and a combination thereof. The drugs usefiil in the present invention are those drugs lliat possess the pharmaceutical property selected fixim the group consisting of antimitotic, dkylating, antimetabolite, antibiotic, alkaloid, antiangiogenic, apoptotic agents and combinations thereof More specifically, these drugs are selected from the group consisting of nitrogen mustards, ethylenimine derivatives, alkyl sulfonates, nitrosoureas, triazenra, folic acid analogs, COX-2 inhibitors, pyrimidine analogs, purine analogs, antibiotics, enzymes, epipodophyllotoxins, platinmn coordination complexes, vinca alkaloids, substituted ureas, methyl hydrazme derivatives, adrenocortical suppressants, antagonists, endostatin, taxols, camptothecins, anthracyclines, taxanes, and their analogs, and a combination thereof The toxins encompassed by the present invention are bacterial, plant, or animal toxins, such as those selected from the group consisting of ricin, abrin, alpha toxin, saporin, onconase, i.e., ribonuclease (RNase), DNase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, diphtheria toxin, Psevdomonas exotoxin, and Pseudomonas endotoxin. Suitable immimomodulators for the present invention include cj'tokine, a stem cell growlh factor, a lymphotoxin, a hematopoietic factor, a colony stimulating factor (CSF), an interferon (IFN), erythropoietin, thrombopoietin and a combination feereof. More specifically lymphotoxins, including tumor necrosis factor (TW), hematopoietic factors, including interleukin(IL-l, IL-2, IL-3, lL-6, IL-10, IL-12, \L-18), colony stimulating factor, including granulocyte-colony stimulating factor (G-CSF) or granulocyte macrophage-colony stimulating factor (GM-CSF)), interferon, including interferons-o, -P or -, and stem cell growth factor, including designated "SI factor." Particularly usefiil therapeutic immunoconjugates comprise one or more radioactive labels tiiat have an energy between 60 and 700 keV. Such radioactive labels mclude, but ar not Hmited to P, "P, ""Sc, 59Fe, "Cu. "Cu, "Se, "As, "Sr, , »Mo. i". '"d, "'Ag. '"I, "'I. 'Pr, '«Pr. '«Pm, 'Sm, 'Tb, 'Ho, '*«&, '"Lu, 'Re. '««Re, ", ', 'Au, '«Au. ="Pb, '¥b, 'Bi, 'Co, "Ga, ""'r, '"-Tc. """ '*Pt, "V '"Sb. 'I, 'Ho, 'Os,'% 'Dy, "At,="=Bi, Ra, 2'Rn, 2"Po. "Bi, Ac, 'Fr, "At, ""Bi and "Fm. and combinations thereof. Other usefiil therapeutic conjugates are photoactive therapeutic agent, such as a chromogen or dye. The present invention particularly encompasses methods of treating hepatocellular carcinoma, hepatoblastoma, germ cell tumors, and other AFP-producing tumors in a. subject such as a mamrmi, including humans, domestic ox companion p&s such as dogs and cats, comprising administraing to the subject a therapeutically effective amount of an anti-AFP MAb or a firagment thereof of the present invention, formulated in a phamiaceutically acceptable vehicle. Prefeibly the anti-AFP antibody or frment hereof is an Immu31 antibody or fragment thereof. This therapy utilizes a "naked antibody" that does not have a therapeutic agent bound to it. The administration of the "naked ImmuS 1 antibody" can be supplemented by administering to the subject concurrently or sequentially a therapeutically effective amount of at least one other "naked antibody" that binds to or is reactive with another antigen on the surface of the target cell or that has other functions, such as effector functions in tiie Fc portion of the MAb, that is therapeutic and vrfiich is discussed herein. For example, prefen:ed MAbs that can supplement the naked Immu31 antibody are humanized, chimeric, human or murine (in the case of non-human animals) carcinoma associated antibothes or fiBgments thereof. Such carcinoma associated antibothes or fragments thereof preferably are selected from the groiq> consisting of a MAb reactive with CEA, EGP-1, EGP-2 (e.g., 17-1 A). MUC-1, MUC-2, MUC-3, MaC-4, PAM-4, K:C4, TAG-72. EGFR, HER2/neu, BrE3, Le-Y, A3, )-CAM, Tn, and Thomson-Friedemeich antigens, tumor necrosis antigens, tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectm, and other vascular growth factors, Ga 733, ferritm and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof Both the naked hnmu31 antibody therapy alone or in combination witii other naked MAbs or fragments thereof as discussed above can be further supplemented with the administration, either concurrently or sequentially, of a therapeutically effective amount of at least one therapeutic agent, formulated in a phamiaceutically acceptable vehicle. As discussed herem the therapeutic agent may comprises a cytotoxic agent, a radioactive label, an immunomodulator, a hormone, a photoactive therapeutic agent or a combination thereof formulated in a phaimaceutically acceptable vehicle. In another therapeutic metho4 both tiie naked Immu31 therjy alone or m combination with otiier naked MAbs, as discussed above, can be further sujiemented with the administration, either concurrentiy or sequentially, of a tha'jeutically effective amount of at least one therutic immunoconjugate, described herein and formulated in a pharmaceutically acceptable vehicle. The therapeutic immunoconjugate comprises at least one humanized, chimeric, human or murine (for non-human subjects) MAb selected from the group consisting of a MAb reactive with CEA, EGP-1, EGP-2 (e., I7-1A), MUC-1, MUC-2, MUC-3, MUC-4. PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friede/ireich antigens, tumw neccosis antigens, tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothelium growth fector (VEGF), placental growth factor (PIGF), ED-B fibronectin, and other vascular growth factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof The therapeutic inununoconjugate may be conjugated to at least one therapeutic agent selected from the group consisting of a cytotoxic agent, a radioactive label, an immunomodulator, a hoimone, a photoactive tfierapeutic agent or a combination thereof, formulated in a pharmaceutically acceptable vehide. As described herein the jaesent invention particurlarly encompasses a mhod of treating a hqiatocellnlar carcmoma, hepatoblastoma, gemi cell tumors, and other AFP producing tumors in a subject comprising administering to a subject a theiapeutically effective amount of an antibody fusion protein or fragment thereof comprisii at least two anti-AFP MAbs or fragments thereof of the present invention or comprisii at least one anti-AFP MAb or fragment thereof of Ac present mvention and at least one carcinoma associated MAb. Preferably, the carcinoma associated antibody is selected from the group consistmg of MAbs reactive wilh CEA, EGP-1, EGP-2, (e.g., I7-1A), MUC-1, MUC-2, MUC-3. MUC-4. PAM-4, KC4, TAG-72, EGFR, HER2/neu. BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necoDsis antigeos, tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR~1, tumor angiogenesis antigens, such as vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectin, and agamst other vascidar wth fectors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combmation thereof Preferably, the anti-AFP antibody or fragment thereof is an Immu31 antibody or fragment thereof * Tins therapeutic method can furlher be supplemented with the administration to the subject concurrently or sequentially of alherKutically effective amount of at least one therapeutic agent, formulated in a pharmaceutically acceptable vehicle, wtherein the therapeutic agent is preferably a cytotoxic agent, a radioactive label, an immunomodulator, a hormone, a photoactive thwapeutic agent or a combination thereof, formulated in a phannaceutically acceptable vehicle. Further, the antibody fiision proteins and fragments thereof of the present invention can be administered to a subject concun-ently or sequentially with a tfierapeutically effective amount of a therwutic conjugate comprising at least one MAb bound to at least one therapeutic agent, wherein smd MAb component of the conjugate preferably comprises at least one humanized, chimeric, human or murine (for non-human subjects) MAb selected from the group consisting of a MAb reactive with CEA, EGP-!, EGP'2 (e.g.. 17-lA), MUC-1, MUC-2, MUC-S, MUC, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, EpAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigens, tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectm, and other vascular growtfi factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof. The antibody fiision protein itself may also be conjugated to at least one therapeutic agent. These therapeutic agents can be a combination of different recited agents or combinations of the same agents, such as two different therapeutic radioactive labels. Also encompassed by the present invention is a method of diagnosing/detecting hepatoceHuIar carcinoma, hepatoblastoma, germ ceJI (uraois, and other AFP producix tumors in a subject conrisii administerit to the subject, such as a mammal, including humans and domestic and companion pets, such as dogs, cats, rabtats, guinea pigs, a diagnostic/detection immimoconjugate comprising an anti-AFP MAb or fiagment thCTCof or an anti-AFP fiision protein or fragment thereof of the present invention that binds to Ihe AFP eqjressing cell, wherein Ihe anti-AFP MAb or figment thercof or antibody fiision protein or fiagment ther«)f is bound to at least one diagnostic/detecti(Hi agent The anti-AFP antibody, fiision protein, or fiagment thereof is preferably an Immu31 antibody, fiision protein, or fi-ment thereof. Optionally, the diagnostic/detection inununoconjugate is formulated in a pharmaceutically acceptable vehicle. The use&l diagnostic ents are described herein. 2. Definitions In the description that follows, a number of terms are used and the following definitions are provided to facilitate understanding of the present invention. An antibody, as described herein, refers to a iull-length (i.e., naturally occurring or formed by noimal immunoglobulin gene fiagment lecombinatorial processes) inunimoglobulin molecule {e.g., an IgG antibody) or an inununologically active (i.e., specifically binding) portion of an immunoglobulin molecule, like an antibody fragment An antibody fi-agment is a portion of an antibody such as F(ab')2, F(ab)3,'Fab', Fab, Fv, sFv and the like. Regardless of structure, an antibody fiagment binds with the same antigen that is recognized by the intact antibody. For example, an anti-AFP monoclonal antibody fiagment binds with an epitope of AFP. The term "antibody fiagment" also includes any synthetic or genetically engineered protein that acts like an antibody by binding to a specific antigen to form a complex. For example, antibody fragments include isolated fragments consistii of the variable regions, such as the "Fv" fragments consisting of tiie variable regions of frie heavy and light chains, recombinant single chain polypeptide molecules in which light and heavy variable regions are connected by a peptide linker ("scFv proteins"), and minimal recognition units consisting of the amino acid residues that mimic the hypervariable region. A naked antibody is generally an entire antibody which is not conjugated to a therapeutic agent. This is so because the Fc portion of the antibody molecule provides effector fiinctions, such as complement fixation and ADCC {antibody dependent cell cytotoxicity), wWch set mechanisms into action that may result in (»11 lysis. Naked antibothes include bo1h polyclonal and monoclonal antibothes, as well as certain recombinant antibothes, such as chimeric, humanized or human antibothes. However, it is possible tfcit the Fc portion is not required for therapeutic function, rather an antibody exerts its therapeutic effect through other mechanisms, uch as induction of cell cycle restir and apoptosis. hi this case naked antibothes also include the imconjugated antibody fragments defined above. A chimeric antibody is a recombinant protein that contains the variable domains including the complementarity determining regions (CDRs) of an antibody derived from one species, preferably a rodent antibody, while the constant domains of the antibody molecule is derived from those of a human antibody. For veterinary applications, the constant domains of the chimeric antibody may be derived from that of other species, such as a cat or dog. A humanized antibody is a recombinant protein in vftdch the CDRS from an antibody from one species; e.g., a rodent antibody, is transferred fiwm the heavy and light variable chains of the rodent antibody into humeui heavy and light variable domains. The constant domains of the antibody molecule is derived fix>ra those of a human antibody. A human antibody is an antibody obtained from transgenic mice that have been "engineered" to produce specific human antibothes in response to antigenic challenge. In this technique, elements of the hiunan heavy and light chain locus are introduced into strains of mice derived from embryonic stem cell lines that contain taieted disruptions of the endogenous heavy chain and light chain loci. The transgenic mice can synthesize human antibothes specific for human antigens, and the mice can be used to produce human antibody-secreting hybridomas. Methods for obtaming human antibothes from transgenic mice are described by Green et al, Nature Genet. 7:13 (1994), Lonberg etal. Nature 368:%56 (1994). and Taylor efa/,. Int. Immun. 6:519 (1994). A frilly human antibody also can be constructed by genetic or chromosomal transfection methods, as well as phage display technology, all of which are known in the art See for example, McCafferty et al. Nature 348:552-553 (1990) for the production of human antibothes and fragments thereof HI vitro, from immimoglobulin variable dommn gene repertoires from unimmunized donors. In this technique, antibody variable domain genes are cloned io-fiame into either a major or minor coat protein gene of a filamentous bacteriophage, and displayed as fimctional antibody fragments on the surface of the phage particle. Because the filamentous particle contains a single-stranded DNA copy of the phage genome, selections based on the fimctional properties of the antibody also result in selection of the gene encoding the antibody exhibiting those properties. In this way, the phage mimics some of the properties of the B cell. Phage display can be performed in a variety of formats, for their review, see e.g. Johnson and Chiswell, Current Opiniion in Structural Biology 3:5564-571 (1993). Human antibothes may also be generated by in vitro activated B cells. See U.S. Patent Nos. 5,567,610 and 5,229,275, which are incoporated in their entirety by reference. A therapevrtic aeent is a molecule or atom which is administered separately, concurrently or sequentially with an antibody moiety or conjiated to an antibody moiety, i.e., antibody or antibody fragment, or a sub&agment, and is useful in thfe treatment of a disease. Examples of therapeutic agents include antibothes, antibody fiagments, drugs, toxins, nucleases, hormones, immunomodulators, chelators, boron compounds, photoactive agents or dyes and radioisotopes. A diagnostic agent is a molecule or atom which is administered conjiated to an antibody moiety, i.e., antibody or antibody ftagment, or subfiragment, and is useful in diagnosing a disease by locating the cells containing the antigen. Useful diagnostic agents include, but are not limited to, radioisotopes, dyes (such as with the biotin-streptavidin complex), contrast agents, fluorescent compounds or molecules and enhancing agents (e.g. paramagnetic ions) for magnetic resonance imaging dRI). U.S. Patent No, 6,331,175 describes MRI technique and the preparation of antibothes conjugated to a MRI enhancing agent and is incoporated in its entirety by reference. Preferably, the diagnostic agents are selected from the group consisting of radioisotopes, enhancing agents for use in magnetic resonance imaging, and fluorescent compunds. In order to load an antibody component with radioactive metals oi paramagnetic ions, it may be necessary to react it witii a reagent Imvii a long tail to which are attached a multiplicity of chelating groups for binding the ions. Such a tail can be a polymer such as a polylysine, polysaccharide, or other derivatized or derivatizable chain having pendant groups to which can be bound chelating groups such as, e.g., ethylenediaminetetraacetic acid (EDTA), thetiiylenetriaminepentaacetic acid (DTPA), porphyrins, polyamines, crown ethers, bis-thiosemicarbazones, polyoximes, and like groups known to be useful for this purpose. Cheles are coupled to the antibothes using standard chemistries. The chelate is normally linked to the antibody by a group which enables formation of a bond to the molecule with minimal loss of immunoreactivity and minimal aggregation and/or internal cross-linking other, more unusual, methods and regents for conjugating chelates to antibothes are disclosed in U.S. Patent 4,824,659 to Hawthorne, entitled "Antibody Conjugates," issued April 25,1989, the disclosure of vWch is incorporated herein hi its entirety by reference. Particularly useful metal-chelate combinations include 2-benzyl-DTPA and its monomethyl and cyclohexyl analogs, used with diagnostic isotopes in the general energy range of 60 to 4,000 keV, such as '"l, 'l, 'I, 'I, «Cu,«Cu, >«F,"V*V'Ga,c,"Tc, "C, 'H '=0,'«Br, forradio-imagmg. The same cheles, when complexed with non-Tadioactive metals, such as manganrae, iron and gadolmium are usefiil for MRI, when used along with the antibothes of the invention. Macrocyclic chelates such as NOTA, DOTA, and TETA are of use with a variety of metals and radiometals, most particularly with radionuclides of gallium, yttriimi and copper, respectively. Such metal-chelate complexes can be made very stable by tailoring the ring size to the metal of interest Other ring-type chelates such as macrocyclic polyetiiers, wWch are of interest for stably binding nuclides, such as Ra for RAIT are encompassed by the invention. An immunoconiugate is a conjugate of an antibody component with a therapeutic or diagnostic agent. The diagnostic agent can comprise a radioactive or non-radioactive label, a contrast agent (such as for magnetic resonance imping, computed tomography or ultrasound), and the radioactive label can be a amraa-, beta-, alpha-, Auger electron-, or positron-emitting isotope. An immunomodulator is a therapeutic agent as defined in the presit invention that when present, typically stimulates immune cells to proliferate or become activated in an immune response cascade, such as macrophages, B»Us, and/or T cells. An example of an immunomodulator as described herein is a cytokine. As the skilled artisan will understand, certain interleukins and interferons are examples of cytokines that stimulate T cell or other immune cell proliferation. An expression vector is a DNA molecules comprising a gene that is expressed in a host cell. Typically, gene expression is placed under the control of certain regulatory elements, including constimtive or inducible promoters, tissue-specific regulatory elements and enhancers. Such a gene is said to be "operably linked to" the regulatory elements. A recombinant host may be any prokaiyotic or eukaryotic cell that contains either a cloning vector or expresaon vector. This term also inclvdes those prokaryotic or eukaryotic cells, as well as an transgenic animal, that have been genetically engineered to contain the cloned gene(s) m the chromosome or genome of the host cell or cells of the host cells. Suitable mammalian host cells include myeloma cells, such as SP2/0 cells, and NSO cells, as well as Chinese Hamster Ovary (CHO) cdls, hybridoma cell lines and other mammalian host cell usefiil for expressing antibothes. Also particularly useful to express MAbs and other fusion proteins, is a himian cell line, PER.C6 disclosed in WO 0063403 A2, which produces 2 to 200-fold more recombinant protein as compared to conventional mammalian cell lines, such as CHO, COS, Vero, Hela, BHK and SP2- cell lines. Special transgenic animals vnth a modified immune system are particularly useful for making fully human antibothes. As used herein, the term antibody fiision protein is a recombinantly produced antigen-binding molecule in which two or more of the same or different natural antibody, single-chain antibody or antibody fragment segments with the same or different specificities are linked. An anti-AFP fusion protein comprises an aipha-fetoprotein bindir site. Preferably, the anti-AFP fiision protein is an Immu31 fiision protein. The Immu31 fusion protein and fi-agment thereof of the present invention comprise at least one arm that binds to the same AFP epitope an antibody or antibody Augment comprising CDRl of a heavy chain variable region that comprises an amino acid sequence of SYVIH, CDR2 of a heavy chain variable region that comprises an amino acid sequence of YIHPYNGGTKYNEKFKG, CDR3 of a heavy chain variable region that comprises an amino acid sequence of SGCKJDPFAY, and CDRl of a light chain variable region that comprises an amino acid sequence of KASQDINKYIG, CDR2 of a light chain variable region that comprises an amino acid sequence of YTSALLP, and CDR3 of a light chain variable region that comprises an amino acid sequence of LQYDDLWT. Valency of the fiision protein indicates the total nximber of binding amis or sites the fusion protein has to antigen(s) or epitope(s); i.e., monovalent, bivalent, trivalent or mutlivalent The multivalency of the antibody fusion protein means that it can take advantage of multiple interactions in binding to an antigen, thus increasing the avidity of binding to the antigen, or to different antigens. Specifici indicates how many different types of antigen or epitope an antibody fusion protein is able to bind; i.e., monospecific, bispecific, trispecific, multispecific. Using these definitions, a natural antibody, e.g., an IgG, is bivalent because it has two binding arms but is monospecific because it binds to one type of antigen or epitope. A monospecific, multivalent fiision protein has more than one binding site for the same antigen or epitope. For example, a monospecific diabody is a fusion protein with two bindii sites reactive with the same antigen. The fusion protein may comprise a multivalent or multispecific combination of different antibody components or multiple copies of the same antibody component. The fiision protein may additionally comprise a therapeutic agent. Examples of therq)eutic agents suitable for such fiision proteins include immunomodulators ("antibody-immunomodulator fusion protein") and toxins ("antibody-toxin fiision protein"). One preferred toxin comprises a ribonuclease (RNase), preferably a recombinant RNase. A multispecific antibody is an antibody that can bind simultaneously to at least two targets that are of different stmcture, e.g., two different antigens, two different epitopes on the same antigen, or a hapten and an antigen or epitope. One specificity would be for, for example, a B-cell, T-cell, myeloid-, plasma-, or mast-cell antigen or epitope. Another specificity could be to a different antigen on the same cell type, such as CD20. CD19, CD21, CD23. CD46, CD80, HLA-DR, CD74, or CD22 on B-cells. Multispecific, multivalent antibothes are constructs that have more than one binding site, and the binding sites are of different specificity. For example, a bispecific diabody, vrfiere one binding site reacts with one anten and the other with another antigen. A bispecific antibody is an antibody that can bind simultaneously to two targets which are of different structure. Bispecific antibothes (bsAb) and bispecific antibody Segments (bsFab) have at least one arm that specifically binds to, for example, a B-cell, T-ceil, myeloid-, plasma-, and mast-cell antigen or epitc and at least one other arm that specifically binds to a targetable conjugate tiiat bears a therapeutic or diagnostic agent A variety of bispecific fiision proteins can be produced using molecular engineering. In one form, the bispecific fiision protein is divalent, consisting of, for example, a scFv witii a siie binding site for one antigen and a Fab fragment with a single binding site for a second antigen. In another form, the bispecific fiision protein is tetravalent, consisting of, for example, an G with two binding sites for one antigen and two identical scFv for a second antigen. Caninized or felinized. antibothes are recombinant proteins in which rodent (or another species) complementarity determining regions of a monoclonal antibody (MAb) have been transferred fi-om heavy and light variable chains of rodent (or another species) immunoglobulin into a dog or cat, respectivety, immunoglobulin variable domain. Domestic animals include large animate such as horses, cattie, sheep, goats, llamas, alpacas, and pigs, as well as companion animals. In a prefared embodiment, the domestic animal is a horse. Companion animals include animals kept as pets. These are primarily dogs and cats, alttiou small rodents, such as guinea pigs, hamsters, rats, and ferrets, are also included, as are subhuman primates such as monkeys, bx a preferred embodiment the companion animal is a dog or a cat. 3. Preparation of Monoclonal Antibothes including Chimeric, Humanized and Human Antibothes Monoclonal antibothes (MAbs) are a homogeneous population of antibothes to a particular antigen and the antibody comprises only one type of antigen binding site and binds to only one epitope on an antigenic determinant. Rodent monoclonal antibothes to specific antigens may be obtained by methods known to those skilled in the art. See, for example, Kohler and Milstein, Nature 256: 495 (1975), and Coligan etal. (eds.), CURRENT PROTOCOLS IN IMMUNOLOGY. VOL. 1,pages 2.5.1-2.6.7 (John WUey & Sons 1991) [hereinafter "Coligan'l. Briefly, monoclonal antibothes can be obtained by injecting mice with a composition comprising an antigen, verifying the presence of antibody production by removing a serum sample, removing the spleen to obtain B-lymphocytes, fusing the B-lymphocytes with nyeloma ceils to produce faybridomas, cloning the hybridomas, selecting positive clones which produce antibothes to the antigen, culturing the clones that produce antibothes to the antigen, and isolating the antibothes fiom the hybridoma cultures. MAbs can be isolated and purified from hybridoma cultures by a variety of well-established techniques. Such isolation techniques include affinity chromatography with Protein-A Sepharose, size-exclusion chromatography, and ion-exchange chromatography. See, for example, Coligan at pages 2.7.1-2.7.12 and pages 2.9.1-2.9.3. Also, seeBadnes et al„ "Purification, of Immunoglobulin G (IgG)," in METHODS IN MOLECULAR BIOLOGY. VOL. 10. pages 79-104 (The Humana Press, Inc. 1992). Abs to peptide backbones are generated by well-known methods for Ab production. For exanqile, injection of an immunogen, such as (peptideVKLH, wherein KLH is keyhole limpet hemocyanin, and n=l-30, in complete Freimd's adjuvant, followed by two subsequent injections of the same immunogen suspended in incomplete Freimd's adjuvant into immunocompetent animals. The animals are given a final i.v. boost of antigen, followed by spleen cell harvesting three days later. Harvested spleen cells are then fijsed with Sp2/0-Agl4 myeloma cells and culture supematants of the resulting clones analyzed for anti-peptide reactivity using a direct-binding ELISA. Fine specificity of generated Abs can be analyzed for by using peptide fi-agments of the original immunogen. These fi:agments can be prepared readily using an automated peptide synthesizer. For Ab production, enzyme-deficient hybridomas are isolated to enable selection of fiised cell lines. This technique also can be used to raise antibothes to one or more of the chelates comprising the linker, e.g., In(III)-DTPA chelates. Monoclonal mouse antibothes to an In(III)-di-DTPA are known (Barbet '395 supra). After the initial raising of antibothes to the immunogen, the variable genes of the monoclonal antibothes can be cloned from the hybridoma cells, sequenced and subsequently prepared by recombinant techniques. Humanization and chimerization of murine antibothes and antibody fragments are well known to those skilled in the art. For example, humanized monoclonal antibothes are produced by transferring mouse complementary determining regions from heavy and light variable chains of the mouse immunoglobulin into a human variable domain, and then, substituting human residues in the fiBmeworit regions of the murine counterparts. In a preferred embodiment, some human residues in the framework regions of the humanized anti-AFP antibody or fragments thereof are replaced by their murine counterparts. Preferably, the humanized anti-AFP antibody is a humanized Immu31 antibody. It is also preferred that a combination of frame woric sequences &oin 2 different human antibothes are used for VH- Still prefenred, the two human antibothes are EU aiul NEWM. The constant domains of the antibody molecule is derived fit)m those of a human antibody. The use of antibody components derived from humanized monoclonal antibothes obviates potential problems associated with the immun(enicity of murine constant rons. General techniques for clonii murine immunoglobulin variable domains are described, for example, by the publication of Orlandi etaL. Proc. Nat'lAcad. Set, USA 86: 3833 (1989), \\Wch is incorporated by reference in its entirety. Techniques for constructing chimeric antibothes are well known to those of skill in the art. As an example, Leung et al, Hybridoma 13:469 (1994), describe how they produced an LL2 chimera by combining DNA sequences encoding the V and VH domains of LL2 monoclonal antibody, an anti-CD22 antibody, with respective human K and IgGi constant region domains. This publication also provides the nucleotide sequences of the LL2 light and heavy chain variable regions, V and VH, respectively. Techniques for producing humanized MAbs are described, for example, by Jones et al., Nature 321: 522 (1986), Riechmann et al. Nature 332: 323 (1988), Verhoeyen et al. Science 239:1534 (1988), Carteret a/., Proc. Nat'lAcad. Sci. USA 89:42S5 (1992),,Sandhu, Crit. Rev. Biotech 12:437 (1992), and Singer e/a/., J. Immufu 150:2844 (1993), each of which is hereby incorporated by reference. Another method for producirg the antibothes of the present invention is by production in the milk of transgenic livestock. See, e.g., Cohnan, A., Biochem. Soc. Synip., 63:141-147,1998; U.S. Patent 5,827,690, both of which are incoporated m their entirety by reference. Two DNA constructs are prepared which contain, respectively, DNA segments encoding paired immunoglobulin heavy and lit chains. The DNA segments are cloned into expression vectors which contain a promoter sequence that is preferentially expressed in mammary epithelial cells. Examples incittde, but are not limited to, promoters from rabbit, cow and sheep casein genes, the cow a-lacfoglobulin gene, the sheep P-lactoglobuIin gene and the mouse whey acid protein gene. Preferably, the inserted fiagment is flanked on its 3' side by cognate genomic sequences firom a mammary-specific gene. This jarovides a polyadenylation site and transcript-stabilizing sequences. The expression cassettes are coinjected into tiie pronuclei of fertilized, mammalian eggs, vrtiich are then implanted into the uterus of a recipient female and allowed to gestate. After birth, the progeny are screened for the presence of both transgenes by Southern analysis. In. order for the antibody to be present, both heavy and light chain genes must be expressed concurrently in the same cell. Milk from transgenic females is analyzed for the presence and fimctionali of the antibody or antibody iragment using standard immunological methods known in the art The antibody can be purified from the milk \ising standard methods known in the art. A chimeric antibody is a recombinant protein that contains the variable domains including the CDRs derived from one species of animal, such as a rodent antibody, while the remainder of the antibody molecule; i.e., the constant dommns, is derived from a human antibody. Accordingly, a chimeric monoclonal antibody lAb) can also be humanized by replacing the sequences of the murine FR in the variable domains of the chimeric MAb with one or more different human FR. Specifically, mouse CDRs are transferred from heavy and light variable chains of the mouse immunoglobulin into the corresponding variable domains of a human antibody. As simply transferring mouse CDRs into human FRs oftai results in a reduction or even loss of antibody afimily, additional modification might be required in order to r«tore tfae original aflSnity of the murine antibody. This can be accomplished by the replacement of oQB or more human residues in the FR regions wi& their murine counteiparts to obtain an antibody that possesses good bindii affinity to its epitope. See, forexanile, Tempest etal., Biotechnology 9:266 (1991) and Veihoeyen et al.. Science 239:1534 (1988). Further, the affinity of humamzed, chimeric and human MAbs to a lecific epitope can be increased by mutagenesis of the CDRs, so diat a lower dose of antibody may be as effective as a higher dose of a lower affinity MAb prior to mutagenesis. See for example, WO0029S84A1. A fully human antibody of the present invention, i.e., a human anti-AFP MAb or another human antibody, such as anti-CEA, anti-TAG-72, anti-Tn, anti-Le(y), anti-MUCl, anti-MUC2, anti-MUC3, anti-MUC4, anti-EGFR, anti-HER2 and anti-TNF (tumor necrosis factor) used for combination therapy with humanized or chimeric Immu31 antibothes, can be obtained fiom a transgenic non-human animal. See, e.g., Uendezetal., Nature Genetics, 15: 146-156 (1997) andU.S. Patent No. 5,633,425, wiiich are incoporated in their entirety by reference. For example, a human antibody can be recovered from a transgenic mouse possessing hiunau immunoglobulin loci. Preferably, the anti-AFP antibody isan ImmuS 1 antibody. The mouse humoral immune system is humanized by inactivating the endtenous immunoglobulin genes and introducii hiunan immunoglobulin locL The human immunoglobulin loci are exceedingly complex and comprise a large number of discrete seents wch together occupy almost 0.2% of the human genome. To ensure that transgenic mice are capable of producing adequate repertoires of antibothes, large portions of human heavy- and light-chain loci must be introduced into the mouse genome. This is accomplished in a stepwise process beginning with the formation of yeast artificial chromosomes (YACs) containing either human heavy- or light-chain immuncobulin loci in germline configuratioii. Since each insert is approximately 1 Mb in size, YAC construction requires homologous recombination of overlpii fragments of tiie immunoglobulin loci. The two YACs, one containing the heavy-chain loci aiwl one containing the light-chwn loci, are introduced separately into mice via fiosion of YAC-containing yeast spheroblasts with mouse embryonic stem cells. Embryonic stem cell clones are then microinjected into mouse blastocysts. Resulting chimeric males are screened for their ability to transmit the YAC through their germline and are bred with mice deficient in murine antibody production. Breeding the two transgenic strains, one containing the human heavy-chain loci and the other containing the human light-chain loci, creates progeny which produce human antibothes in response to inununization. Unrearranged human immunoglobulin genes also can be introduced into mouse embryonic stem cells via microcell-mediated chromosome transfer (MMCT). Seff>e.g.,Tomzoka.etal., Nature Genetics, 16: 133(1997). In this methodology microcells containing human cliromosomes are fused with mouse embryonic stem cells. Transferred chromosomes are stably retained, and adult cWmeras exhibit proper tissue-specific expression. As an alternative, an antibody or antibody fragment of the present invention may be derived from human antibody fragments isolated from a combinatorial immunoglobulin library. See, e.g., Barbas etal, METHODS: A Coirmiion to ' Methods in Emymology 2: 119 (1991), and Winter et al, Ann. Rev. Immunol 12:433 (1994), which are incorporated by reference. Many of Ihe difficulties associated with generating monoclonal antibothes by B-cell immortalization can be overcome by engineering and expressing antibody fragments in E. coli, usmg phage display. To ensure the recovery of high affinity, monoclonal antibothes a combinatorial immunoglobulin library must contain a large repertoire siw. A typical strategy utilizes mRNA obtained from lymphocytes or spleen cells of immimized mice to synthesize cDNA using reverse transcriptase. The heavy- and lit-chain genes are amplified separately by PCR and ligated into phage cloning vectors. Two different libraries are produced, one containing the heavy-chain enes and one containing the light-chain genes. Phage DNA is islolated from each library, and the heavy-and light-chain sequences are ligated together and packaged to form a combinatorial library. Each phage contains a random pair of heavy- and light-chain cDNAs and iqwn infection of £■- coli directs the expression of the antibody chains in infected cells. To identify an antibody that recognizes the antigen of interest, the phage library is plated, and the antibody molecules present in the plaques are transferred to filters. The filters are incubated with radioactively labeled antigen and then washed to remove excess unbound ligand. A radioactive spot on the autoradiogram identifies a plaque that contains an antibody that binds the antigen. Clonii and expression vectors that are usefiil for producing a human immunoglobulin phage library can be obtned, for example, from STRATAGENE Cloning Systems (La JoUa, CA). Further, recent methods for producing bispecific MAbs include engineered recombinant MAbs which have additional cysteine residues so that tlwy crosslink mwe strongly than the more common immunoglobulin isotypes. See, e.g., FitzGerald et oL, Protein Eng. 10(10):122l-1225,1997. AnotlierapiaxjachistoengiiKerrecombmant fusion proteins linking two or more different single-chain antibody or antibody fragment segments with the needed dual specificities. See, e.g., Coloma et al., Nature Biotech. 15:159-163,1997. A variety ofbispecific fusion proteins con be produced using molecular engineering. In one form, the bispecific fusion protein is monovalent, consisting of, for example, a scFv with a single binding site for one antigen and a Fab fragment with a single binding site for a second antigen. In another form, the . bispecific fusion protein is divalent, consisting of, for example, an IgG with two binding sites for one antigen and two scFv with two binding sites for a second antigen. 6i>eci&c fusion proteins linking two or more diffoent single-chain antibothes or antibody fragmoits are produced in similar manner. R«Mmbiiwnt methods can be used to produce a variety of fusion proteiiui. For ejaunple a fusion protein cotnprisii a Fab fragment derived from a humanized monoclonal Immu31 antibody and a scFv derived from a murine anti-diDTPA can be produced. A flexible linker, such as GOGS connects the scFv to the constant region of the heavy chain of the hnmu31 antibody. Alternatively, the scFv can be connected to the constant region of the light chain of another humanized antibody. Appropriate linker sequences necessary for the in-frame connection of the heavy chain Fd to the scFv are introduced into the VL and VK domains through PCR reactions. The DNA frjnent encoding the scFv is then ligated into a staging vector containing a DNA sequence encoding the CHI domain. The resultmg scFv-CHl construct is excised and ligated into a vector containing a DNA sequence encoding the VH region of an Immu31 antibody. Tlie resulting va::tor can be used to iransfect an appropriate host cell, such as a mammalian cell for the expression of the bispecific fusion protein. Preparation of chimeric, humanized and human anti-AFP antibothes Cell lines and culture media used in the present invention include immu31 hybridoma cells and Sp2/0-Agl4 myeloma cells (ATCC, Rockville, MD). The monoclonal hybridoma producing Iinmu31 was obtained by fusing the spleen cells prepared from a mouse that had been immunized with alpha-fetoprotein with SP2/0AgH. These cells may be cultured in Hybridoma serum-free media (HSFM) (life Technologies, Grand Island, NY) supplemented with 10% fetal bovine saxim (FBS) (Hyclone Laboratories, Logan, LTT) and antibiotics (complete media). Alternatively, they may be cultured in Dulbecco's modified Eagle's Medium (DMEM) supplemented with 10% FCS (Gibco/BRL, Gaithersburg, Mass.) contaming 10% of FCS and 75 ng/ml gantamicin (complete HSFM) or, where mdicated, in HSFM containing only antibiotics. Selection of the transfectomas may be carried out in complete HSFM containing 500 units/ml of hygromycin (Calbiochem, San thego, CA). All cell lines are preferably maintained at 37° C in 5% COi- Obtaining VKOJtd VH Gene Segmeitts Isolation of tiie VK and VH gene segments can be accomplished by several means that are Avell-known in the art Two such means include, but are not limited to, PCR cloning and cDNA library screening. PCR cloning techniques are well-known in the art In brief, however, PCR cloning of VK and VH gene fi-agments may be accomplished as follows. Total RNA may be isolated from a Immu31 hybridoma cell line using commercially available kits such as the Fast Track RNA Isolation kit (Invitrogen, San thego, CA). The first strand cDNA may then be reverse transcribed from RNA using a cDNA cycle Idt (Invitrogen). In this process, 5 jig of total RNA is annealed to an oligo dT or random hexamer primer, or a murine IgG CHI-specific primer or a murine Ck-specific primer. Examples of such primers include CHIB (5' - ACA GTC ACT GAG CTG G - 3') and Ck3-BH1 (5'- GCC GGA TCC TGA CTG GAT GGT GGG AAG ATG GAT ACA - 3'), respectively. The first strand cDNA may be used as templates to aniliiy the VH and VK sequences by PCR, as described by Orlandi et al. For the VK region, a primer pair such as VKIBACK (5' - GAC ATT CAG CTG ACC CAG TCT CCA - 3') and IgKC3' (5' - CTC ACT GGA TOG TGG GAA GAT GGA TAC AGT TGG - 3') may be used. For the VH region, aprimer pair such as VHIBACK (5' -AGG T(C/GXA/C) A(A/G)C TGC AG(C/G) AGT C(AJT)G G- 3') and CHIB may be used. After amplification, the VK and VH fragments may then be gel-purified and cloned into a cloning vector such as the TA cloning vector (Invitrogen) for sequence analyses by the dideoxyteraiination method. Sequences confinned to be of immunoglobulin origin may then be used to construct chimeric Ab expression vectors using methods described by Leung et al. (Hybridoma, 13:469 (1994)). As a preferred alternative to isolating the VK and VH gene segments by PCR cloning, cDNA library screening may be utilized. cDNA screening methods also are well known in the art In brief, however, a cDNA library may be coitftructed fiom the mRNA extracted from the murine Immu31 hybridoma cells in pSPORT vectbr (Life Technologies). The first strand cDNA may be synthesized by priming ply A RNA from hiimu31 hybridoma with an oligo dT primer-NotI adaptor (Life Technologies). After the second strand synthesis and attachment of Sal! adaptors, the cDNA pool may be size fractionated through a cDNA size fractionation column. Fractionated cDNA may thenbe ligated to pSPORT vector and subsequently transfoimed into Escherichia cob' DH5a. A library may then be plated, transferred to filters, and ampliSed. Screening of the cDNA library may be accomplished by hybridization with labeled probes specific for the heavy and light chains. For example [32-P]-labeled probes such as MUCH-1 (5' - AGA CTG CAG GAG AGC TGG GAA GGT GTG CAC - 3') for heavy chain and MUCK-1 (5' - GAA GCA CAC GAC TGA GGC ACC TCC AGA TGT - 3') for light chain. Clones that are positive on a first screening may be transferred to duplicate plates and screened a second time with the same probes. RMA isolation, cDNA synthesis, and amplification can be carried out as follows. Total cell RNA can be prepared from a Immu31 hybridoma cell line, using a total of about lO' cells, according to Sambrook et al., (Molecular Cloning: A Laboratory Manual, Second ed., Cold Spring Harbor Press, 1989), which is incorporated by reference. First strand cDNA can be reverse transcribed from total RNA conventionally, such as by using the Superscript preamplification systen (Gibco/BRL, Gaithersburg, Md.). Briefly, in a reaction volume of 20 jal, 501 of random hexamer primers can be aimealed to 5 p,g of RHAs in the presence of 2 pi of lOX synthesis buffer [200 mM Tris-HCl (pH 8.4), 500 mM KCl, 25 mM MgCla, 1 mg/ml BSA], I fd of 10 mM dNTP mbc, 2 1 of 0.1 M DTT, and 200 units of Superscript reverse transcriptase. The elongation step is initially allowed to proceed at room temperature for 10 min followed by incubation at 42" C. for 50 min. The reaction can be terminated by heating the reaction mixture at 90° C. for 5 mjn. Synthesizing and labeling the screening probes can be accomplished by well-known means. Depending on the detection systems utilized, probe labeling will vary. Many kits for this pxupose are commercially available. One method for 32-P labeling of oligonucleotides includes the use of with [Y-"'P]ATP (Amersham Ariington Heights, IL) and T4 polynucleotide kinase (New England Biolabs, Beverly, MA), follovcd by column purification. Preparation of a chimeric anti-AFP antibody In general, to prepare chimeric anti-AFP MAb, VH and VK chains of a AFP antibody may be obtained by methods such as those described above and amplified by PCR. In a preferred embodiment, the chimeric aati-AFP antibody is a ImmuSl antibody. The VK PCR products may be subcloned into a pBR327 based stng vector (VKpBR) as described by leung et al., Hybridoma, 13:469 (1994). The VH PCR products may be subcloned into a similar pBluescript-based staging vector (VHpBS). The fiagments containing the VK and VH sequences, along with the promoter and signal peptide sequences, can be excised from the staging vectors using Hindm and BamHI restriction endonucleases. The VK fiagments (about 600 bp) can be subcloned into a mammalian expression vector (for example, pKh) conventionally. pKh is a pSVhyg-based expression vector containing the genomic sequence of the human kappa constant region, an Ig enhancer, a kappa enhancer and the hygromycin-resistant gene. Similarly, the about 800 bp VH frments can be subcloned into pGlg, a pSVgpt-based expression vector canying the genomic sequence of the human IgGi constant region, an Ig enhancer and the xanthine-guanine phosphoribosyl transferase (gpt) gene. The two plasmids may be co-transf«sed into mammalian cdls, such as Sp2/0-Agl4 cells, by electroporation and selected for hygromycin resistance. Colonies surviving selection are expanded, and supernatant fluids monitored for production of clmmu31 MAb by an ELISA method. A transfection efficiency of about 1-10 X 10 cells is desirable. An antibody expression level of between 0,10 and 2.5 tig/ml can be expected with this svstem. Alternately, the VK and VH expression cassettes can be assembled in the modified staging vectors, VKpBR2 and VHpBS2, excised as Xbal/BamHI and XhoI/BamHI fragments, respectively, and subcloned into a single expression vector, such as pdHL2, as described by Gilles et al J. Immunol Methods 125:191 (1989), Losman eJ" a/., C//n. Cancer s. 5:1101 (1999) aadrntasmanetal.. Cancer 80:2660 (1997) for the expression m Sp2/0-Agl4 cells. Another vector that is useful in the present invention is the GS-vector, as described in Barnes et al., Cytotedmology 32:109-123 (2000), which is preferably expressed in the NSO cell line and CHO cells. Other appropriate mammalian expression systems are described in Werner et a/., Aizneim.-Forsch./Drug Res. 48(11), Nr. 8, 870-880 (1998). Preparation of a humanized ajiti-AFP antibody In a preferred embodiment, the humanized anti-AFP antibody is a humanized Immu31 antibody. Once the sequences for the hlmmu31 VK and Vfj domains are designed, CDR engrafting can be accomplished by gene synthesis using long synthetic DNA oligonucleotides as templates and short oligonucleotides as primers in a PCR reaction, hy most cases, the DNA encoding the VK or VH domain will be approximately 350 bp long. By taking Ewivantie of codon degeneracy, a unique restriction site may easily be introduced, without changing the encoded amino acids, at regions close to the middle of the V gene DNA sequence. For example, at DNA nucleotide positions 169-174 (ammo acid positions 56-57) for the hlmmu31 VH domain, a imique Kpnl site can be introduced while maintaining the originally designed amino acid sequence (see the sequence in Figure 5A). Two loi non-overlapping single-stranded DNA oligonucleotides (~ 150 bp) upstream and downstream of the Kpnl site can be generated by autonmted DNA digoaucleotide synthesizer (Cyclone Plus DNA Synthesizer, Milligen-Biosearch). As the yields of full length DNA oligonucleotides may be expected to be low, they can be amplified by two pairs of flanking oligonucleotides in a PCR reaction. The primers can be designed with the necessaiy restriction sites to fecilitate subsequent sequence assembly and subcloning. Primers for the oligonucleotides should contain overlapping sequence at the Kpnl site so that the resultant PCR products can be joined in-ftame at the Jnl site to form a full length DNA sequence encodii the hlmmu31 VH domain. The ligation of the PCR products for the oligos at the Kpnl site and their subcloning mto the Pstll/BstEII sites of the staging vector, VHpBS, can be completed in a single three-firagment ligation step. The subcloning of the correct sequence into VHpBS can be first analyzed by restriction digestion analysis and subsequently conformed by sequencing reaction according to Sanger et al., Proc. Natl. Acad. Sci. USA 74 5463 (1977). The Hindm/BamHI fragment containing the Ig promoter, leer sequence and the hhnmu31 VH sequence can be excised from the staging vector and subcloned to the corresponding sites in a pSVgpt-based vector, pGlg, which contains the genomic sequence of the human IgG constant region, an Ig enhancer and a'gpt selection marker, forming the final ejq)ression vector, hlmmuSlpGIg. Similar strategies can be employed for the construction of the hlmmu31 VK sequence. The restriction site chosen for the ligation of the PCR products for the long oligonucleotides can be Nsil in &is case. The DMA sequence containing the Ig promoter, leader sequence and the hlmmnSl VK sequence can be excised from the staging vector VKpBR by treatment with BamHI/Hindin, and can be subcloned into the corresponding sites of a pSVhyg-based vector, pKh, vhich contains the genomic sequence of human kappa chain-constant regions, a hygromycin selection marker, an Ig and a kappa enhancer, forming the final expression vector, hlmmu3 IpKh. The two plasmids can be co-transfected into an qipropriate cell, e.g., myeloma Sp2/0-Agl4, colonies selected for hygromycin resistance, and supernatant fluids monitored for production of hlmmu31 antibothes by, for example, an ELISA assay, as described below. Ahemately, the VK and VH expression cassettes can be assembled in the modified staging vectors, VKpBR2 and VHpBS2, excised as Xbal/BamHI and XhoI/BamHI fiagments, respectively, and subcloned into a single expression vector, such as pdHL2, as described by Gilles etal.,J. Immunol. Methods 125:191 (1989), Losman et al., Clin Cancer Res. 5:3101 (1999) and in Losman et al.. Cancer, 80:2660 (1997) for the expression in Sp2/0-Agl4 cells. Another vector that is useful in the present invention is the GS vector, as described in Barnes et al., Cylotechiiology 32:109-123 (2000), which is preferably expressed intheNSO cell line and CHO cells. Other appropriate rnammalian expression systems are described in. Werner et al., Ar2neim.-ForschyDrug Res. 48(11), Nr. 8, 870-880 (1998). Transfection, and assay for antibody secreting clones by ELISA, can be carried out as follows. About 10 ng of hImmu31pKh (light, chain expresaon vector) and 20 ng of hlmmuSlpGlg (heavy chain expression vector) can be used for tiie traiKfection of 5 -x 10 SP2/0 myeloma cells by electroporation (BioRad, Richmond, Calif) accordmg to Co et al., J. Immimol., 148:1149 (1992) which is mcorporated by reference. Following transfection, cells may be grown in 96-well microtiter plates in complete HSFM medium (GIBCO, Gaithersburg, Md.) at 37" C.,'5% COz. The selection process can be initiated after two days by the addition of hygromycin selection medium (Calbiochem, San thego, Calif) at a final concentration of 500 g/ml of hygromycin. Colonies typically emerge 2-3 weeks post-electroporation. The cultures can then be expanded for further analysis. Screening the Clones and Isolating Antibothes Transfectoma clones that are positive for the secretion of chimeric or humanized heavy ch2»in can be identified by ELISA essay. Briefly, supernatant samples (100 (il) from transfectoma cultures are added in triplicate to ELISA microtiter plates precoated wathoat anti-human (GAH)-IgG, F(ab')2 fragment-specific antibody (Jackson ImmxmoResearch, West Grove, Pa.). Plates are incubated for 1 h at room temperature. Unbound proteins are removed by \TOshing three times with wash buffer (PBS containing 0-05% polysorbate 20). Horseradish peroxidase (HRP) conjugated GAH-IgG, Fc fragment-specific antibothes (Jackson fmmunoResearch, West Grove, Pa.) are added to the wells, (100 pi of antibody stock diluted X 10**, supplemented with the unconjugated antibody to a final concentration of 1.0 fig/ml). Following an incubation of 1 h, the plates are washed, typically three times. A reaction solution, [100 pi, containing 167 (xg of orthophenylene-diamine (OPD) (Sigma, St. Louis, Mo.), 0.025% hydrogen peroxide in PBS], is added to the wells. Color is allowed to develop in the dark for 30 minutes. The reaction is stopped by the addition of 50 ]i\ of 4 N HCl solution into each well before measuring absorbance at 490 nm in an automated ELISA reader (Bio-Tek instruments. Winooski, Vt). Bound chimeric antibothes are than deteimined relative to an irrelevant chimeric antibody standard (obtainable from Scotgen, Ltd., Edinburg, Scotland). Antibothes can be isolated from cell cuJture media as follovre. Transfectoma cultiires are adapted to serum-free medium. For production of chimeric antibody, cells are grown as a 500 ml culture in roller bottles using HSFM. Cultures are centrifriged and the supernatant filtered through a 0.2 micron membrane. The tered medium is passed throi a protein A column (1x3 cm) at a flow rate of I ml/min. The resin is then washed with about 10 column volumes of PBS and protein A-bound antibody is eluted from the column with 0.1 Mglycine buffer (pH 3.5) containing 10 TOMEDTA. Fractions of 1.0 ml are collected in tubes containing 10 of3MTris (pH 8.6), and protein concentrations detemiined from the absorbancies at 280/260 mn. Peak fractions are pooled, dialyzed against PBS, and the antibody concentrated, for example, with the Centricon 30 (Amicon, Beverly, Mass.). The antibody concentration is determined by ELISA, as before, and its concentration adjusted to about 1 mg/ml using PBS. Sodium azide, 0,01 % (w/v), is conveniently added to the sample as preservative. The affinity of a chimeric, humanized or human anti-AFP antibody may be evaluated using a direct binding assay or a competitive binding assay. Modifying/Optimizing the Recombinant Antibothes As humanization sometimes results in a reduction or even loss of antibody affinity, additional modification might be required in order to restore the original affinity (See, for example. Tempest et al., Bio/Technology 9: 266 (1991); Verfioeyen et al., Science 239:1534 (1988)), which are incorporated by reference. Knowing tiiat clnimu31 exhibits a bindii affim'ty comparable to that of its murine counteipart, defective designs, if any, in the original version of hImmS 1 u can be identified by mixing and matching the light and heavy chains of clnmiu31 to those of the himianized version. Preferably, some human residues in the frameworic regions are replaced by their murine counterparts. Also preferred, a combination of framework sequences from 2 different human antibothes, such as EU and XWM are used for VH. For example, FRl-3 can come from EU and FR 4 from NEWM. Other modifications, such as Asn-linked glycosylation sites, can be introdueced into a chimerized, human, or humanized Iinmu31 antibody by conventional oligonucleotide directed site-specific mutenesis. Detailed protocols for oligonucleotide-directed mutagenesis and related techniques for mutagenesis of cloned DNA are well known. For example, see Sambrook et al. and Ausubel et at above. For example, to introduce an Asn in position 18 of WmmuSl VK (figure 4B), Alternatively, an Asn-linked glycosylation site can be introduced into an antibody light chain using an oligonucleotide containing the desired mutation as the primer and DNA clones of the variable regions for the Vk chain, or by using RNA from cells that produce the antibody of interest as a template. Also see, Huse, in ANTIBODY ENGINEERINGr A PRACTICAL GUIDE, Boerrebaeck, ed., W. H. Freeman & Co., pp. 103-120,1992. Site-directed mutagenesis can be perfomied, for example, using the TRANSFORMER™ kit (Clonetech, Palo Alto, Calif.) accotding to tlie manufacturer's instructions. Alternatively, a gJycosylation site can be introduced by synthesizing an antibody chain with mutually priming oligonucleotides, one such containing the desired mutation. See, for example, Uhlmann, Gene 71; 29 (1988); Wosnick et al., Gene 60:115 (1988); Ausubel et al., above, which are incorporated by reference. Although the general description above referred to the introduction of an Asn giycosylation site in position 18 of the light chain of an antibody, it will occur tothe skilled artisan that it is possible to introduce Asn-linked giycosylation sites elsewhere in the light chain, or evea in fiie heavy chain variable ron. 4. Frodudioii of Antibody Fragments Antibody fragments which recognize specific epitopes can be generated by known techniques. The antibody fragments are antigen binding poitions of an antibody, such as F(ab')2, Fab', Fab, Fv, sFv and the like. Other antibody fragments include, but are not limited to: tiie F(ab)'2 fragments which can be produced by pepsin digestion of the antibody molecule and the Fab' fragments, wiiich can be generated by reditting disiilfide bridges of tiie F(ab)'2 fragments. Alternatively, Fab' expression expression libraries can be constructed (Huse et al, 1989, Science, 246:1274-1281) to allow nid and easy identification of monocIotKl Fab' fragments with the desired specificity. The present invention encompasses antibothes and antibody fragments. A single chmn Fv molecule (scFv) comprises a VL domain and a VH domain. The VL and VH domains associate to form a taiet bindii site. These two donmins are ftirther covalently linked by a peptide linker (L). A scFv molecule is denoted as either VL-L-VH if the VL domain is the N-terminal part of tiie scFv molecule, or as VH-L-VL if the VH domain is the N-terrainal part of the scFv molecule. Metiiods for making scFv molecules and designing suitable peptide linkers are described in US Patent No. 4,704,692, US Patent No. 4,946.778, R. Raag and M. Whitiow, "Single ChainFvs." FASEB Vol 9:73-80 (1995) andR.E. Bird and B.W. Walker, "Single Chain AiUibody Variable Regions," TIBTECH, Vol 9: 132-137(1991). These references are incorporated herein by reference. To obtain high-afSnity scFv, an scFv library with a large repertoire can be constructed by isolating V-genes from non-immunized human donors using PCR primers corresponding to ail knovm VH, V and Vi gene families. See, e.g., Vau et ai, Nat. Biotechnoi, 14: 309-314 (1996). Following amplification, the V and V pools are combined to form one pool. These fragneuts are ligated into a phagemid vector. The scFv linker, (Gly-GIy-Gly-Gly- Ser)3, is then ligated into the phagemid upstream of the VL fitigment The VH and linker-VL fhments are amplified and assembled on the JH region. The resulting VH-linker-VL fragments are ligated into a phagemid vector. The phagemid library can be panned using filters, as described above, or using immunotubes (Nunc; Maxisoip). Similar results can be achieved by constructing a combinatorial immunoglobulin library from lymphocytes or teen cells of immunized rabbits and by expressing the scFv constructs in P. pastoiis. See, e.g., Ridder e/ al.. Biotechnology, 13: 255-260 (1995). Additionally, followii isolation of an appropriate scFv, antibody fragments with higher binding affinities and slower dissociation rates can be obtained through affinity maturation processes such as CDR3 mutagenesis and chain shufthng. See, e.g., Jackson et ah, Br. J. Cancer, 78: 181-188 (1998); Osboum et al., Immunoiechnology, 2:181-196 (1996). An antibody fragment can be prepared by proteolytic hydrolysis of the full leith antibody or by expression in E. coli or another host of the DNA cotUng for tiw fragment An antibody fragment can be obtained by pepsin or papain digestion of fiill length antibothes by conventional methods. For example, an antibody fragment can be produced by en2ymatic cleavage of antibothes with pepsin to provide a 100 Kd fragment denoted F(ab')2. This fragment can be further cleaved using a thiol reducii agent, and optionally a blocking group for the sulfbydryl groups resulting fipm cleavage of disulfide linkages, to produce SO Kd Fab' monovalent figments. Alternatively, an enzymatic cleavse using papain produces two monovalent VeSo fragments and an Fc fragment directly. These methods are described, for example, by Goldenberg, U.S. Patent Nos. 4,036,945 and 4,331,647 and references contained therein, \\4uch patents are incorporated herein in their entireties by reference. Also, see Nisonoff e/ al. Arch Biochem. Biophys. 89: 230 (1960); Porter, Biochem. J. 73: 119 (1959), Edehnan et al.. in METHODS IN E3ZYM0L0GY VOL. 1, page 422 (Academic Press 1967). and Coligan at pages 2.8.1-2.8.10 and 2.10.-2.10.4. Another fonn of an antibody fragment is a peptide coding for a single complementarity-determinii region (CDR). A CDR is a segment of the variable region of an antibody that is complementary in structure to the epitope to wiiich the antibody binds and is more variable than the rest of the variable region. Accordingly, a CDR is sometimes referred to as hypervariable region. A variable region comprises three CDRs. CDR peptides can be obtained by constructing genes encoding the ,CDR of an antibody of interest. Such genes are prepared, for example, by using the polymerase chain reaction to synthesize the variable region from RNA of antibody-producing cells. See, for example, Larrick et al.. Methods: A Companion to Methods in Enzymology 2:106 (1991); Courtenay-Luck, "Genetic ManipuJadon of Monoclonal Antibothes," m MONOCLONAL ANTIBOtheS: PRODUCTION, ENGINEERING AND CLINICAL APPLICATION, Ritter et al. (eds.), pages 166-179 (Cambridge University Press 1995); and Ward et al, "Genetic Manipulation and Expression of Antibothes," in MONOCLONAL ANTIBOtheS: PRINCIPLES AND APPLICATIONS, Birch et al, (eds.), pages 137-185 (Wiley-Liss, Inc. 1995). Other methods of cleaving antibothes, such as separation of heavy chains to form monovalent light-heavy chain fragments, further cleavage of fragments, or other en2yroatic, chemical or genetic techniques may also be used, so long as the frments bind to the antigen that is recognized by the intact antibody. 5. Fusion proteins The antibody ftision proteins of the present invention comprise two or more antibothes or fragments thereof and each of the antibothes that compose this fiision protein can contain a therapeutic agent or diagnostic agent. In other words, the antibody frision protein or fragment thereof can comprise at least one first anti-AFP MAb or fragment thereof and at least one second MAb or fragment thereof that is not an anti-AFP MAb. In a preferred embothement, the anti-AFP antibody or fragment thereof is an Immu31 antibody or fragment thereof. Preferably, the second MAb is a carcinoma-associated antibody, such as an antibody agamst CEA, EGP-1, EGP-2 (e.g., I7-IA), MUC-1, MUC-2, MUC-3, MUC-4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigens, tumor necrosis antigens, tenascin, an oacogene, an oncogene product, IL-6, IGF-l, IGER-I, tumor angiogenesis antigens, such as vascular endotiielium growth factor (VEGF), placenta] growth factor (PIGF), E0-B fibronectin, and other vascular growth factors, Ga 733, 17-1 A, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof. Additionally, one or more of the antibothes or frments thereof that comprise the antibody fusion protein can have at least one therapeutic or diagnostic/detection agent attached. Further, the diagtuistic/detection agents or therKUtic agents need not be the same but c£Ui be different therapeutic agaits; for example, one can attach a dri and a radioisotope to the same fiision protein. Pwticulary, an IgG can be radiolrfieted ■with'l and attached to a dn. The 'l can be incorporated into the tyrosine of the IgG and tl drug attached to the eion amino group of the IgG lysines. Both therTcutic and dinostic agents also can be attached to reduced SH groups and to the carbohydrate side chains. Also preferred, the antibody fusion protein of the present invention comprises at least two anti-AFF monoclonal antibothes or fragments thereof, and these may be to different epitopes of the alphafetoprotein antigen or of different human immunoglobulin backbone sequences (or IgGs). Preferably, the anti-AFP antibothes or fragments there of are ImmuSl antibothes or fragments thereof. Muliispecijic and multivalent antibothes In another embodiment of the instant invention is a conjited multivalent ImmuSl antibody. Compositions and methods for multivalent, multispecific agents are described in Rossi et al., U.S. Patent Application Serial No: 6(V436,359, filed December 24,2002, and US Patent Application serial No. 60/464,532, filed April 23, 2003, which are incoiporated herein by reference in its entirety. The Inunu31 antibothes and fragments thereof of the present invention, as well as other antibothes with different specificities for use in combination therapy, can be made as a multiecific antibody, comprising at least one binding site to an alpha fetoprotein antigen and at least one binding site to another tigen, or a multivalent antibody comprising multiple binding sites to &e same epitope or antigen. In a preferred embodiment, the multispecific antibody or fi:ment thereof comprises at least one binding site to an ImmuS 1 epitope and at least one binding site that is not to lie AH* antigen. ThelmmuSl epitope is an epitope on the AFP antigen that is recognized by the Immu31 antibothes of the present invention. Also preferred, the multispecific antibody or fragment thereof comprises at least one binding site to an Immu31 epitope and at least one binding site to a different epitope on the AFP antigen. Tlie present invention provides a bispecific antibody or antibody fragment having at least one binding region that specifrcally binds AFP and at least one other binding region that specifically binds another targeted cell maricer or a targetable conjiate. The targetable conjugate comprises a carrier portion vMch comprises or bears at least one epitope recognized by at least ope binding region of the bispecific antibody or antibody fragment Preferably, the bispecific antibody binds to an ImmuSl epitope in the AFP antigen. A variety of recombinant methods can be used to produce bi-specific antibothes and antibody fi:agments. For example, bi-specific antibothes and antibody fi-agments can be produced in the milk of transgenic livestod See, e.g., Colman, A., Biochem. Soc. Symp., 63: 141-147,1998; U.S. Patent No. 5,827,690. Two DNA constructs are prepared which contain, respectively, DNA segments encodii paired immunoglobulm heavy and light chains. The fragments are cloned into expression vectors which contain a promoter sequence that is preferentially expressed in niammaty epithelial cells. Examples include, but are not limited to, promoters from rabbit, cow and sheep casein genes, the cow a-lactoglobulin gene, the sheep p-lactoglobulin gene and the mouse whey acid protein gene. Preferably, the inserted fragment is flanked on its 3* side by cognate genomic sequences fix)m a mammary-specific gene. This provides a polyadenylation site and transcript-stabilizing sequences. The expression cassettes are coinjected into the pronuclei of fertilized, niammalian eggs, which are then implanted into the uterus of a recipient female and allowed to gestate. After birth, the progeny are screened for the presence of both transgenes by Southern analysis. In order for the antibody to be present, both heavy and light chain genes must be expressed concurrently in the same cell. Milk fr-om transgenic females is analyzed for the presence and fiinctionality of the antibody or antibody fragment using standard immunological methods known in the art. The antibody can be purified from the milk using standard methods known in the art Other recent methods for producing bsAbs include engineered recombinant Abs which have additional cysteine residues so that they crosslink more strongly than the more common immunoglobulm isolypes. See, e.,FitzGeralde/a/., Protein Eng. IO(10):122I-1225,1997, Another approach is to engineer recombinant fiision proteins linking two or more different single-chain antibody or antibody frsment segments with the needed dual specificities. See, e.g., Coloma et al, Nature Biotech. 15:159-163,1997. A variety of bi-specific frision proteins can be produced using molecuiai engineering. In one form, the bi-specific fiision protein is monovalcDt, consisting of; for example, a scFv with, a single bindii site for one antigen and a Fab fiagment with a single binding site for a second antigen. In another form, the bi-specific fiision protein is divalent, consisting of, for example, an IgG with two binding sites for one antigen and two scFv with two binding sites for a second anten. An anti-AFP multivalent antibody or fragment therwjf is also contemplated m the present invention. Preferably, the anti-AFP multivalent antibody or fiment thereof is an Immu31 multivalent antibody or fragment thereof. This multivalent antibody is constructed by association of a first and a second polypeptide. The first polypeptide comprises a first single chain Fv molecule covalently linked to a first immimoglobulin-like domain wliich preferably is an immunoglobulin light chain variable region domaiiL The second polypeptide comprises a second single chain Fv molecule covalently linked to a second immunogiobulin-like domain which preferably is an immunoglobulin heavy chain variable region domain. Each of Ibe first and second single chain Fv molecules forms a target binding site, and tiK first and second immunoglobulin-like domains associate to form a third target binding site. A single chain Fv molecule vnth the VL-L-VH configuration, wherein L is a linker, may associate with another single chain Fv molecule with the VH-L-VL configuration to form a bivalent dimer. In this case, tte VL domam of the first scFv and the VH domain of the second scFv molecule associate to forni one target binding site, wiiile the VH domain of the first scFv and the VL domain of the second scFv associate to forai the other target binding site. Another embodiment of the present invention is an Imnm31 bispecific, trivalent antibody comprising two heterologous polypeptide chains associated non-covalently to form three binding sites, two of which have affinity for one taiget and a third wliich has afBnity for a hapten that can be made and attached to a carrier for a diagnostic and/or therapeutic agent. Preferably, the antibody has two Inunu31 binding sites and one CEA or MUCl binding site. The bispecific, trivalent targeting agents have two different scFvs, one scFv contains two VH domains from one antibody comiected by a short linker to the VL domain of another antibody and the second scFv contains two VL domains from the first antibody connected by a short linker to fee VH domain of the other antibody. The methods for generating multivalent, multispecific agents Gxan VH and VL domains provide that individual chains synthesized from a DNA plasmid in a host organism are composed entirely of VH domains (the VH-chain) or entirely of VL tk)mains (the VL-chain) in such a way that any agent of miiltivalency and multispecificity can be produced by non-covalent association of one VH-chain with one VL-chain. For example, fomiing a trivalent, trispecific agent, the Vn-chain will consist of the amino acid sequences of thrw VH domains, each from an antibody of different specificity, joined by peptide linkers of variable lengths, and the Vt-cluiin will consist of complementary VL domains, joined by peptide linkers similar to those used for the VH-chain. Since the VH and Vi, domains of antibothes associate in an anti-parallel fashion, the preferred method in this invention has the VL domains in the Vt-chain arranged in the reverse order of the VH domains in the Vn-chain. Diabothes, Triabothes and Tetrabothes The anti-AFP antibothes and fragments thereof of the present invention can also be used to prepare fimctional bispecific single-chain antibothes (bscAb), also called diabothes, and can be produced in mammalian cells using recombinant methods. Preferably, the anti-AFP antibody or fragment thereof is an Inmm31 antibody or fragment thereof See, e.g.. Mack et ah, Proc. Natl. Acad. Scl, 92: 7021-7025,1995, incorporated. For example, bscAb are produced by joining two single-chain Fv figments via a glycine-serine linker using recombinant methods. The V light-chain (VL) and V heavy-chain (VH) domains of two antibothes of interest are isolated using standard PCR methods. The VL and VH CDNA'S obtained £rom each hybridoma are then joined to form a single-chain fiagment in a two-step &sion PCR. The first PCR step introduces the (GIy4-Serj)3 linker, and the second step joins the VL and VH ampJicons. Each single chain molecule is then cloned into a bacterial expression vector. Following amplification, one of the single-chain molecules is excised and sub-cloned into the other vector, containing the srcond single-chain , molecule of interest- The resulting bscAb fiagment is subcloned into an eiiaiyotic exjffession vector. Functional protein e:q>ression can be obtained by transfectii the vector into Chinese hamster ovary cells. Bispecific fusion proteins are prepared in a similar manner. Bispecific single-chain antibothes and bispecific fiision proteins are included within the scope of ttie present invention. For example, a hiunanized, chimeric or human or murine Immu31 monoclonal antibody can be used to produce antigen specific diabothes, triabothes, and tetrabothes. The monospecific diabothes, triabothes, and tetrabothes bind selectively to targeted antigens and as the number of binding sites on the molecule increases, the sffuiity for tl target cell increases and a longer residence time is observed at the desired location. For diabothes, the two chains comprising the VH polypeptide of the humanized Immu3l MAb connected to the VR polypeptide of the humanized hnmu3l MAb by a five amino acid residue linker are utilized. Each chain forms one lalf of tiieh«manizedlromu31 diabody. In the case of triabothes, the three chains comprising VH polypeptide of the humanized ImmuSl MAb connected to the VR polypeptide of the humanized Immu31 MAb by no linker are utilized. Each chain fonns one third of the hImmuBl triabody. Also contemplated in the present invention is a bi-specific antibody or antibody fiagment havii at least one arm that is reactive against a targeted tissue such as AFP and at least one other arm that is reactive gainst a targetable construct. Preferably, one arm of the bispecific antibody binds the Zmmu 31 epitoge. The targetable comtruct is comprised of a carrier portion and at least 2 imits of a recogju2abIe hten. Examples of recognizable hsqitsns include, but are not limited to, histamine succinyl glycine (HSG) aivd fluotrain isothiocyanate. The tiffgetable constmct may be conjugated to a variety of agents usefiil for treating or identifying diseased tissue. The targetable construct can be of diverse structure, but is selected not only to avoid eliciting an immune response, but also for rid in vh'o clearance when used within the bsAb targeting method. Hydrophobic agents are best at eliciting strong immune responses, whereas hydrophilic agents are preferred for rapid in vivo clearance; thus, a balance between hydrophobic and hydrophilic needs to be establisiwd. This is accomplished, in part, by relying on the use of hydrophilic chelating agents to offset the inherent hydrophobicily of many organic moieties. Also, subunits of (he targetable construct may be chosen ch have opposite solution properties, for example, peptides, wdiich contain amino acids, some of wdiich are hydrophobic and some of which are hydrophilic. Aside fiom peptides, carbohydrates may be used. Large qiiantities of bscAb and fiision proteins can be produced usir Escherichia coli expression systems. See, eg., Zhenping et al.. Biotechnology, 14: 192-196,1996. A functional bscAb can be produced by the coexpression in J?. coliof two "cross-over" scFv fiagments in which the Vj, and VH domains for the two fragments are present on different polypeptide chains. The V light-chain (V) and V heavy-chain (VH) domains of two antibothes of interest are isolated using standard PCR methods. The cDKA's are then ligated into a bacterial expression vector such that C-terminus of the "V domain of the first antibody of interest is ligated via a linker to the N-terminus of the VH domain of the second antibody. Similarly, the C-terminus of the VL domain of the second antibody of interest is ligated via a Imfcer to the N-tetminus of the VH domain of tiie first antibody. The resxdting dicistronic operon is placed under transcriptional control of a strong promoter, e.g., the E. coli alkaline phosphatase promoter which is inducible by phosphate starvation. Alternatively, single-chain fijsion constructs have successfully been expressed in E. coli usir the lac promoter and a medium consisting of 2% glycine and 1 % Triton X-100. See, e.g., Yang et al, Appl Environ. Microbiol., 64:2869-2874,1998. An E. coli. beat-stable, enterotoxin II signal sequence is used to direct the peptides to the periplasmic space. After secretion, the two peptide chains associate to form a non-covalent heterodimer which possesses both antigen binding specificities. The bscAb is purified using standard procedures known in the art, e.g.. Staphylococcal inxttein A chromatography. Functional bscAbs and fiision proteins also can be produced in tfie milk of transgenic livestock. See, e.g., Colman, A., Siochem. Soc. Symp., 63:141-147,1998; U.S. Patent No. 5,827,690. The bscAb fragment, obtained as described above, is cloned into an expression vector containii a promoter sequaice that is jweferentiaUy expressed in manmiaiy epithelial cells. Examples include, but are not limited to, promoters from rabbit, cow and sheep casein genes, the cow a-Iactoglobulinene, the sheep P-Iactoglobulin gene and the mouse wliey acid protein gene. Preferably, the inserted bscAb is flanked on its 3' side by cognate genomic sequences from a mammary-specific gene. This provides a polyadenylatiott site and tramcript-stabilizing sequences. The expression cassette is then injected into tlte pronuclei of fertilized, mammalian eggs, Ach are then implanted into Ihe uterus of a recipient female and allowed to gestate. After birth, the progeny are screened for the presence of the introduced DNA by Southem analysis. Milk from transgenic females is analyzed for Hbs presence and functionality of the bscAb using standard immunological methods known in the art. The bscAb can be purified from the milk using standard methods known in the art Transgenic production of bscAb in milk provides an efficient method for obtaJnii large quantities of bscAb. Functional bscAb and fusion proteins also can be prodticed in transgenic plants. See, e.g., Fiedler e/o/.,5/Dtec/(., 13: 1090-1093,1995; Fiedler e/a/., Immunotechnology, 3:205-216,1997. Such production offers several advantages including low cost, large SCBIC o\ut and sfa.ble, long term storage. The bscAb fragment, obtained as described above, is cloned into an expression vector containing a promoter sequence and encoding a signal peptide sequence, to direct fbe protein to the endoplasmic recticulum. A variety of promoters can be utilized, allowing the practitioner to dfrect the expression product to particular locations within the plant For example, ubiquitous expression in tobacco plants can be achieved by usii the strong cauliflower mosaic virus 3SS promoter, while organ specific expression is achieved via the seed specific legumin B4 promoter. The expression cassette is transforaied according to standard methods known in the art Transfonnation is verified by Southem analysis. Transgenic plants are analyzed for the presence and functionality of the bscAb using standard immunological methods known in the art The bscAb can be purified from the plant tissues using standard methods known in the art Additionally, transgenic plants facilitate long term storage of bscAb and fosion proteins. Functionally active scFv proteins have been extracted from tobacco leaves after a week of storage at room temperature. Similarly, transgenic tobacco seeds stored for 1 year at room temperature show no loss of scFv protein or its antigen bindii activity. Functional bscAb and fusion proteins also can be produced in insect cells. See,e.g.,Mahiouzetal., J. Immunol. MethodSy2l2: 149-160(1998). hisect-based eqiression systems provide a means of producing large quantities of homogenous and properly folded bscj. The baculovirus is a widely used expression vector for insect cells and has been successfiilly applied to recombinant antibody molecules. See, e.g., Miller, h.K.,Ann. Rev. Microbiol, 42: 177(1988); Bei etal.,J. Immunol. Methods 186: 245 (1995). Alternatively, an inducible expression system can be utilized by generating a stable insect cell line contmning the bscAb construct under the transcriptional control of an inducible promoter. See, e.g., Mahiouz et ah, J-Immunol Method!, 212:149-160 (1998). The bscAb frment, obtained as described above, is cloned into an expression vector containii tiie Drosphila metallotiuonein promoter and the human HLA-A2 leader sequence. The construct is then transfected into D. melanogaster SC-2 cells. Expression is inducoi by exposing the cells to elevated amounts of copper, zinc or cadmium. The presence and fonctionaiity of the bscAb is determined using standard immunological methods known in the art. Purified bscAb is obtained using standard methods known in the art The ultimate use of the bispecific diabothes described herein is for pre-targeting Immu31 positive tumors for subsequent specific delivery of diagnostic/detection or therapeutic agents. These diabothes bind selectively to targeted antigens allowdng for increased affinity and a longer residence tune at the desired location. Moreover, non-antigen bound diabothes are cleared from the body quickly and exposure of nonnal tissues is minimized. The diagnostic/detection and therapeutic agents can include isotopes, drugs, toidns, cytokines, hormones, growth factors, conjugates, radionuclides, and metals. For example, gadolinium metal is used for magnetic resonance imaging (MRI). Examples of radionuclides are *«Ga, "Ga, ,** Y, "V '"l, ""l. ""l, Tc, "c, '«Re. 'Re, 'Lu. *Cu, "Cu, *'Cu,'Bi,"Bi,P, "C, ', 'O, "Br, and 2" At. Other radionucUdes are also available as diagnostic and therapeutic agents, especially those in the eaeigy raie of 60 to 4,000 keV. More recently, a tetravalent fcindem diabody (tenned tendab) with diud specificity has also been reported (Cochlovius et al.. Cancer Research (2000) 60: 4336-4341). ITie bispecific tandab is a dimer of two identical polypeptides, each containing four variable domains of two different antibothes (VHI, VLI, VHZ, V) linked in an orientation to facilitate the formation of two potential'binding sites for each of the two different specificities upon self-association. 7. ImmiiSl Immunoconjugafes Any of the anti-AFP antibothes or fi-agraents thereof, or antibody fiision proteins or ferments thereof of the present invention can be conjugated with one or more therapeutic and/or diagnostic/detection agents. Generally, one ttierapeutic or diagnostic/detection agent is attached to each antibody or antibody fi-ment but more than one therapeutic agent or diagnostic agent can be attached to the same antibody, fusion protein, or figment thereof. Such a therapeutic or diagnostic/detection ent may be a peptide which beara a diagnostic/detection or therapeutic agent. An immunoconjugate retains the immunoreactivity of the antibody component, i.e., the antibody moiety has about the same or slightly reduced ability to bind Has ctnate antigen after conjugation as before conjugation. A wide variety of diagnostic/detection and therapeutic ents can be advantEeously conjugated to Ae antibody, fusion protein, ot fragment thereof of the present invention, hi a preferred embodiment, the diagnostic/detection ents are selected from the group consisting of radioisotopes for nuclear imaging, intraoperative and endoscopic detection, enhancing agents for use in magnetic resonance imaging or in ultrasonography, radiopaque and contrast agents for X-rays and computed tomography, and fluorescent compounds for fluoroscopy, including endoscopic fluoroscopy. Fluorescent and radioactive agents conjugated to antibothes or used in bispecific, pretargeting methods, are particularly useful for endoscopic, intraoperative or intravascular detection of the targeted antigens associated with diseased tissues or clusters of cells, such as malignant tumors, as disclosed in Goldenberg U.S. Pat Nos. 5,716,595,6, 09689 and U.S. Application Serial No. 09/348,818, incorporated herein by reference in their entirety, particulariy with gamma-, beta-, and positron-emitters. Radionuclides useful for positron emission tomography include, but are imt limited to: F-18, Mn-51, Mn-S2m, Fe-S2, Co-55, Cu-62, Cu-64, Ga-68, As-72, Br-75, Br-76. Rb-82m, Sr-83, Y-86, Zr-89, Tc-9'hn, In-110,1-120, and 1-124. The therapeutic agents recited here are those agents that also are useful for administration separately with a naked antibody, as described herein. Therapeutic ag&Os include, for example, chemotherapeutic drugs such as vinca alkaloids and other alkaloids, anthracyclines, epidophyllotoxins, taxanes, antimetabolites, alkylating agents, antibiotics, COX-2 inhibitors, antimitotics, antiangiogenic and apoptotoic agents, particularly doxorubicin, methotrexate, taxol, CPT-11, camptothecans, and others iiom these and other classes of anticaiu agents, and the like. Other useful cancer chemotherapeutic drugs for the preparation of immunoconjiates and antibody fiision proteins include nitrogen mustards, alkyl sulfonates, nitrosoureas, triazenes, folic acid analogs, COX-2 inhibitors, pyrimidine analogs, purine analogs, platinum coordination complexes, hormones, toxins (e.g., RNAse, Psudomonas exotoxin), and the like. Suitable chemotherapeutic agents are described in REMINGTOIrS PHARMACEUTICAL SCIENCES, 19th Ed. (Mack Publishing Co. 1995), and in GOODMAN AND OILMAN'S THE PHARMACOLOGICAL BASIS OF THERAPEUTICS, 7th Ed. (MacMiUan PubUshing Co. 1985), as well as revised editions of these publications. Other suitable chemotherapeutic agents, such as experimental drugs, are known to those of skill in tiie art A toxin, such as Pseudomonas exotoxin, may also be complexed to or form the therqwutic agent portion of an immunoconjugate of the Immu31 antibody or fiagment thereof of the present invention. Additionally, the toxin may be used in combination with a naked ImmuS 1 antibody or fi-ment thereof, an Immu31 fiision protein or fragment thereof, or a Immu31 antibody or fragment thereof conjugated to a different therapeutic agent. Other toxins suitably employed in the preparation of such conjugates or ottier fusion proteins, include ricin, abrin, ribonuctease (RNase), Dlase I, Staphylococcal enterotoxin-A, pokeweed antiviral protein, gelonin, dipbtberin toxin, Pseudomonas exotoxin, and Pseudomonas endotoxin. See, for example, Pastan et al. Cell 47:641 (1986), and Goldenberg, CA - A Caticer Journal for Clinicians 44:43 (1994). Additional toxins suitable for use in the present invention aie known to tlM>se of skill in the art and are diIosed in U.S. Patent No. 6,077,499, which is incorporated in its entirety by reference. These can be derived, for example, from animal, plant and microbial sources, or chemically or recombinantly engineered. The toxin can be a plant, microbial, or animal toxin, or a synthetic variation thereof. An immunomodulator, such as a cytokine may also be conjugated to, or fbnn the therapeutic agent portion of the Iinmu31 inmiunoconiugate, or be administered unconjugated to the chimeric, humanized or huiiuin anti-AFP antibody, fusion protein, or fiagment thereof of the present invention. As used herein, the term "immunomodulator" includes cytokines, stem cellowth ]tors, lymphotoxins, such as tumor necrosis factor (TNF), and hematopoietic factors, such as interleukins (e.g., interleukin-I (IL-1), JL-2, IL-3, lL-6, IL-IO, lL-12 and IL-IS), colony stimulating factors (e.g. granulocyte-colony stimulating factor (G-CSF) and ©lanulocyte macrophagenolony stimulating factor (GM-CSF)), interferons (e.g., interferons-o, -p and -y), the stem cell growth factor designated "SI factor," eiythiopoietin and thrombopoietm. Examples of suitable immunomodulator moieties include lL-2, IL-6, IL-10, IL-12, IL-18, interferon-7, TNF-a, and the like. Altwnatively, subjects can receive a naked Immu31 antibody or fragment thereof, or naked fiision i»t)teui or fragment thereof, and a separately administered cytokine, vMch can be administered before, concurrently or after administration of tiie naked hnmu31 antibody or fragment, or naked Immu31 fusion protein or fragment thereof. The Inunu31 antibody or fragment there or fusion protein or figment tiiereof of may also be conjugated to an immimomodulator. The immunomodulator may also be conjugated to a hybrid antibody consisting of one or more antibothes or antibody fragments binding to different antigens. Such an antigen may also be an immunomodulator. For example, CD40 or other imniunomodulators may be administered in combination with a Iminu31 antibody or fragment thereof either together, before or after the antibody combinations are administered. Furthermore, an hmnu31 antibody or fragment thereof, or fusion protein or fragment thereof may comprise a y-emitting radionuclide or a positron-emitter UisefUl for diagnostic imaging. Examples of diagnostic/detection agents include diveise' labels, radionuclides, chelators, dyes, contrast agents, fluorescent compounds, chromseas, and other imdcer moieties. Radionuclides useful for positroa emission tomography include, but are not Umited io: '*F, 'Mn, ""Mn, "Pe, Co, *Cu, "Cu, «Ga, '"As, "Br, "Br, Rb. '"Sr, '. «*&, 'c, " V "\ and '\ Total decay energies of useful positron-emitting radionuclides aie piefaly Additionally, radionuclides suitable for treating a diseased tissue include, but are not limited to, P-32, P-33, Sc-47, Fe-59, Cu-64, Cu-67, Se-75, As-77, Sr-89, Y-90, Mo-99, Rh-105. Pd-109. Ag-Ul, 1-125,1-131, Pr-142, Pr-143, Pm-149, Sm-153, Tb-161, Ho-166, Er-169, Lu-177, Re-186, Re-188, Re-189, Ir-194, Au-198, Au-199, Pb-211, Pb-212, and Bi-213, Co-58, Ga-67, Br-80m, Tc-99m, Rh-103m, Pt-109. lo-l 11, Sb-Il9,1-125, Ho-161, Os-189m, h--192, Dy-152. At-211, Bi-212, Ra-223, Rn-219, Po-215, Bi-211, Ac-225, Fr-221, At-217, Bi-213 and Fm-255. Suitable diagnostic imaging isotopes are usually in tiie raie of 20 to 2,000 keV, vMle suitable therapeutic radionuclides are usually in the range of 20 to 10,000 keV. See for example, U.S. Patent Application entitled "Labelii Targeting Ageirts with Gallium-68"- Inventors G.L.Griffiths and W.J. McBride, (U.S. Provisional Application No. 60/342,104), which discloses positron emitters, such as F, Ga, "Tc. and the like, for imaging purposes and which is incorporated in its entirety ty reference. A suitable radionuclide is an Auger emitter, and preferably has an enei of less than 1000 keV. Also preferred is a emitter and has an energy between 20 and 5000 keV or an , emitter and has an energy between 2000 and 10,000 keV. A therapeutic or diagnostic/detection agent can be attached at the hinge region of a reduced antibody component via disulfide bond formation. As an alternative, such peptides can be atUiched to the antibody corapoosnt xi&iag a beteawbifoiKtioiml cross-linker, such as JV-succinyl 3-(2-pyridyldithio)proprionate (SPDP). Yu et al, bit. J. Cmicer 56:244 (1994). General techniques for such conjugation are well known in the art. See, for example. Wong, CHEMISTRY OF PROTEB* CONIUGATION AM5 CROSS-LINKING (CRC Press 1991); Upeslacis et al, "Modification of Antibothes by Chemical Methods," in MONOCLCWAL ANTIBOtheS: PRINCIPLES AND APPLICATIONS, Birch et al. (eds.). pages 187-230 (WUey-Liss, Inc. 1995); Price, "Production and Characterisation of Syntiietic Peptide-Derived Antibothes." in MONOCLONAL ANTIBOtheS: PRODUCTION, ENGINEERING AND CLINICAL APPLICATtON, Ritter et al (eds.), pages 60-84 (Cambridge Universi Press 1995). Alternatively, tiie therapeutic or dinostic agent can be conjugated via a carbohydrate moiety in the Fc region of the antibody. The carbohydrate group can be used to increase the loading of the same peptide that is bound to a thiol group, or the carbohydrele moiety can be nsed to bind a different pTtide. Methods for conjugating peptides to antibody components via an antibody carbohydrate moiety are well known to those of skill in the art See, for example, S\aketaL. Int. J. Camer41: 832 (1988); Shihe/a/., bU. J. Cancer 46: UQl (1990); and Shih et ai, U.S. Patent No. 5,057,313, all of which are incorporated in Ibehr entirety by reference. The general method, involves reacting an antibody component having an oxidized carbohydre portion witii a carrier polymer that has at least one free amine fimction and that is loaded with a plurality of peptide. This reaction results in an initial SchifTbasc (iinine) linkage, which can be stabilized by reduction to a secondary amine to form the final conjugate. However, if the Fc region is absent, for example, if the antibody used as the antibody conaeot of the immunoconjugate is an antibody ftagment, it is till possible to attach a diagnostic/detection a therapeutic agent. A carbohydrate moiety can be introduced into the light chain variable region of a fuU-lengUi antibody or antibody fragment See, for example, Leung e? a/., /mmuno/. 75-:5919(1995); Hansen et al, U.S. Patent No. 5,443,953 (1995), Leung et al.. U.S. patent No. 6,254,868, all of which are incoporated in their entirety by reference. The engineered carbohydrate moiety is used to attach the ther)eutic or diagnostic agent Targe/able Constructs The targetable construct can be of diverse structure, but is selected not only to avoid eliciting an immune responses, but also for rapid in vivo clearance when used within ibe bsAb taieting method. Hydrophobic agents are best at eliciting strong immune responses, vAereas hydrophilic ents are preferred for rapid in vivo clearance; thus, a balance between hydrophobic and hydrophiUc needs to be established. This is accomplished, in part, by relying on the use of hydrophilic chelating agents to o£t the inherent hydrophobicity of many organic moieties. Also, subimits of the targetable constmct may be chosen which have opposite solution properties, for example, peptides, which contain amino acids, some of which are hydrophobic and some of which are hydrophilic. Aside from peptides, carbohydrates may be used. Peptides having as few as two amino-acid residue may be used, preferably two to ten residues, if also coupled to other moieties such as chelating agents. The linker should be a low molecular weight conjugate, preferably having a molecular weight of less than 50,000 daltons, and advantageously less than about 20,000 daltons, 10,000 daltons or 5,000 daltons, including the metal ions in the chelates. For instance, the known peptide DTPA-Tyr-Lys(DTPA)-OH (wherein DTPA is thethylenetriaminqientaacetic acid) has been used to generate antibothes Jainst the indium-DTPA portion of the molecule. However, by use of the non-indium-containing molecule, and propriate screening steps, new Abs against the tyrosyl-lysine dipeptide can be made. More usually, the antigenic peptide will have fo\ir or more residues, such as the peptide D0TA-Phe-Lys(HSG)-Tyr-Lys(HSG)-NH2, wherein DOTA is 1,4,7,10-tetraazacyclododecanetetraacetic acid and HSG is the histamine succinyl glycyl group of the formula: TTie non-metai-containing peptide may be used as an inunuccen, with resultant Abs screened for reactivity against the Phe-Lys-Tyr-Lys backbone. The invention also contemplates the incorporation of unnatural amino acids, e,g., D-amino acids, into the backbone structure to ensure that, ven used with the final bsAh/linker system, the arm of the bsAb wiiich recognizes the linker moiety is completely specific. The invention further contemplates other backbone structures such as those constructed from non-natural amino acids and peptoids. The peptides to be used as immunogens are synthesized conveniently on an automated peptide synthesizer using a solid-phase support and standard techniques of repetitive orthogonal deprotection and couplii. Free amino groups in the peptide, that are to be used later for chelate conjugation, are advantageously blocked with standard protecting groups such as an acetyl group. Such protecting groups will be known to the skilled artisan. See Greene and Wuts Protective Groups in Organic Synthesis, 1999 (John Wiley and Sons, N.Y.). When the peptides are prepared for later use within the bsAb system, they are advantageously cleaved from the resins to generate the corresponding C-tenninal amides, in order to inhibit in vivo carboxypeptidase activity. The haptens of the inununogen comprise an immunogenic recognition moiety, for example, a chemical hapten. Using a chemical hapten, preferably tfie HSG hten, hi specificity of the linker for the antibody is exhibited. This occurs because antibothes raised to the HSG hapten are known and can be easily incorporated mto the appropriate bispecific antibody. Thus, btng of the linker with the attached hapten would be highly specific for the antibody or antibody figment. Chelate Moieties The presence of hydrophilic chelate moieties on the linker moieties helps to ensiue rapid in vivo clearance. In addition to hydropliilicity, chelators are chosen for their metal-bindmg properties, and are changed at will since, at least for diose linkers whose bsAb epitope is part of the peptide or is a non-chelate chemical hapten, recognition of the metal-chelate complex is no longer an issue. A chelator such as DTP A, DOTA, TET A, or NOTA or a suitable peptide, to ■which a detectable label, such as a fluorescent molecule, or cytotoxic ent, such as a heavy metal or radionuclide, can be conjugated. For exanle, a tiierKutically usefiil inununoconjngate can be obtained by conjugating a photoactive agent or dye to an antibody fusion protein. Fluorescent compositions, such as fluorochrome, and other chromog«is, or dyes, such as porphyrins sensitive to visible liit, have been used to detect and to treat lesions by directing the suitable light to the lesion. In theny, this has been termed photoradiation, phototherapy, or photodynamic theny (Jori et aj. (eds.), PHOTODYNAMIC THERAPY OF TUMORS AND OTHER DISEASES (Libreria Progetto 1985); van den Bergh, Chem. Britain 22:430 (1986)). Moreover, monoclonal antibothes have been coupled with photoactivated dyes for achieving phototherapy. Ucw et al., J. Immunol. J30:1473 (1983); idem.. Cancer Res. 5:4380 (1985); OseioSet al, Proc. Natl. Acad. Set USA 55:8744 (1986); idem., Photochem. Photobiol. 46:S3 (1987); Kasmetal., Prog. Clin. Biol. Res. 288:471 (1989); Tatsuta et al. Lasers Surg. Med 9:422 (1989); Pelegrin et d., Cancer 670.529 (1991). However, these earlier stuthes did not include use of endoscopic therapy applications, especially with the use of antibody fragments or subfragments. Thus, the present invention contemplates the therapeutic use of immunoconjiates comprising photoactive agents or dyes. particularly usefiil metal-chelate combinations include 2-benzyl-DTPA and its monomethyl and cyclohexyl analogs, used with "Sc, Fe, "Co, "Oa, 'Oa, "V "% **Y, '*'Tb, '"LU, 'Bi, 'Bi, and "=Ac for radio-imaging and RAIT. The same chelators, when complexed with non-radioactive metals, such as Mn, Fe and Gd can be used for MRI, wen used aloi with the bsAbs of the invention. Mactocyclic chelators such as NOTA (l,4,7-triaza-cyc]ononane-N',N"-triacetic acid), DOTA, and TETA (p-bromoacetamido-benzyl-tetrlhylaminetetraacetic acid) are of use with a variety of metals and radiometals, most particxilarly with radionuclides of Ga, Y and Cu, respectively. Ul f A and DOTA-type chelators, where the UUMI includes hard base chelating functions such as carboxylate or amine groups, are most effective for chelating hard acid cations, especially Group Ha and Group ilia metal cations. Such metal-chelate complexes can be made very stable by tailoring the ring size to the metal of interest. Other ring-type chelators such as macrocyclic polyefhers are of interest for stably binding nuclides such as Ra for RAIT. Porphyrin chelators may be used with numerous radiometals, and are also useful as certain cold metal complexes for bsAb-directed immuno-phototherapy. More than one type of chelator may be conjugated to a carrier to bind multiple metal ions, e.g., cold ions, dinostic radionuclides and/or therapeutic radionuclides. Particidariy useful tiierwutic radionuclides include, but are not limited to, P. ', *c, 'Cu, *'Cu, Ga, , '"Ag. "V '"I. "'I, "'Pr. *»Sm, '*'Tb, '«Dy, 'o. Lu, ". '""Re, '""Re. '¥b. 'Bi, "Bi, "At. Ra and Ac. Particularly usefU diagnostic/detection radionucUdes include, bm are not lunited to, '¥, Fe, Cu, "Cu, *"Cu, "Oa, **Ga, , Zr, "Tc, 'c, **c, '"In, 'I. '\ '"l, 'l, '=«Gd and '"LU. Chelators such as those disclosed in U.S. Patent 5,75306, especially thioseoii-carbazonylglyoxylcysteine (Tscg-Cys) and thiosemicarbazinyl-acetylcysteme (Tsca-Cys) chelators are advantageously used to bind soft acid cations of Tc, Re, Bi and other transition metals, lantbanides and actinides that are ttly bound to soft base ligands, especially suliiir- or phosphorus-containing ligands. It can be usefiil to link more than one type of chelator to a peptide, e,g., a DTPA or similar chelatQC for, say In(ni) cations, trnd a thiol-containii chelator, e.g., Tscg-Cys, for Tc cations. Because antibothes to a di-DTP A hapten are known (Barbet' 395, supra) and are readily coupled to a targeting antibody to form a bsAb, it is possible to use a peptide hapten with cold diDTPA chelator and another chelator for binding a radioisotope, in a pretargeting protocol, for targetuig the radioisotope. One example of such a peptide is Ac-Lys(DTPA)-Tyr-Lys(DTPA)-Lys(Tscg-Cys-)-NH2. This peptide can be preloaded with In(III) and tlien labeled with 99-m-Tc cations, the In(lII) ions being preferentially chelated by the DTPA and the Tc cations binding preferentially to the thiol-contatning Tsc-Cys. Other hsxd acid-chelators such as NOTA, DOTA, TETA and the like can be substituted for the DTPA groups, and Mafas specific to them can be produced using analogous techniques to those used to generate theanti-di-DTPAMab. It will be jpreciated tluit two differait hard acid or soft acid cltelatots can be incorporated into the linker, e.g., with diflfereat chelate ring sizes, to bind preferentially to two different hard acid or soft acid cations, due to the difieiing sizes of the cations, the geometric of the chelate rings aiwi the preferred complex imi structures of the cations. This will permit two different metals, one or both of w4uch may be radioactive or usefiU for MRI enhancement, to be incorporated into a linker for eventual capture by a iffetargeted bsAb. Preferred chelators incliide NOTA, DOTA and Tscg and combinalions thereof. These chelators have been incoiporated into a chelator-peptide conjugate motif as exemplified m tiie foUowii constructs: (a)D0TA-Phe-Lys(HSG>D-Tyr-Lys(HSG)-NH2; (b) D0TA-Phe-Lys(HSG)-Tyr-Lys(HSG)-NH2; (c)Ac-Lys(HSG)D-Tyr-Lys(HSG)-LysCrscg-Cys)-NH2; The chelator-peptide conjugates (d) and (e), above, has been shown to bind Ga antf is thus usefiil in positron emission tom(rhy (PET) application. Chelators are coupled to the linker moieties using standard chemistries which are discussed more fully in the woricing Examples below. Briefly, the synthesis of the peptide Ac-Lys(HSG)D-Tyr-Lys(HSG)-Lys(Tscg-Cys-)-NH2 was accomplished by first attaching Aloc-Lys(Fmoc)-OH to a Rink amide resm on the pitide synthizer. The protecting group abbreviations "Aloe" and "Fmoc" used herem refer to the groups allyloxycarbonyl and fluorenylmethyloxy carbonyl. The Fmoc-Cys(Trt)-OH and TscG were feen added to the side chain of tiie lysine using standard Fmoc automated synthesis protocols to form the following peptide: Aloc-Lys(Tscg-Cys(Trt)-rink resm. The Aloe group was then removed. The peptide synthesis was then continued on the synthesizer to make the following peptide; (Lys(Aloc)-I>-Tyr-Lys(Aloc)-Lys(Tscg-Cys(Trt)-)-rinfc resin. Following N-tenninus acylatioa, and removal of the side chain Aloe protecting groaps. Tbe resulting peptide was then treated with activated N-trityl-HSG-OH imtil the rrain gave a negative test for amines using the Kaiser test See Yiaracay et al Biocougate Chein. ]] •M2-$54 (2000). The synthesis of Ac-Lys(HSG)D-Tyr-LysCHSG)-Lys(Tscg-Cys->NH2, as weU as the syntheses of DOTA-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-NH2; and DOTA-Phe-Lys(HSG>Tyr-Lys{HSG)-NH2 are described in greater detail below. Preparation of Metal Chelates Chelator-peptide conjugates may be stored for long periods as solids. They may be metered into unit doses for metal-bmding reactions, and stored as unit doses eitiier as solids, aqueous or semi-aqueous solutions, fiozen solutions or lyophiliz preparations. They may be labeled by well-known procedures. Typically, a hard acid cation is introduced as a solution of a convenient salt, and is taken up by the hard acid chelator and possibly by the soft acid chelator. However, later addition of soft »;id cations leads to binding thereof by the soft acid chelator, displacii any hard acid cations wiuch may be chelated therein. For example, even in the presence of an excess of cold "'ihCls, labeling with 99m-Tc(V) glucoheptonate or with Tc cations generated in situ with stannous chloride andNa99m-Tc04 proceeds quantitatively on the soft acid chelator. Other soft acid cations such as ' *Rje, '"Re, 'Bi and divalent or trivalent cations of Mn, Co, Ni, Pb, Cu, Cd, Au, Fe, Ag (monovalent), Zn and Hg, especially **Cu and 'Cu, and the like, some of which are useful for radioimmunodiagnosis or radioimmunothery, can be loaded onto the linker peptide by analogous methods. Re cations also can be generated in situ from perrbenate and stannous ions or a prereduced rhenium glucoheptonate or other transchelator can be used. Because reduction of peixhenate requires more stannous ion (typically above 200 pg/niL final concentration) than is needed for the reduction of Tc, extra care needs to be taken to ensure that the higher levels of stwmous ion do not reduce saisitive disulfide bonds such as tiiose present in disulfide-cyclized peptides. During ■: .[diolabeling with rhenium, similar procedures are used as are used with the Tc-99m. A preferred method for the preparation of ReO metal complexes of the Tscg-Cys-ligands is by reacting the peptide with ReOCl3{P(Ph3)2 but it is also possible to use other reduced species such as ReO(ethylenediainine)2. 8. Humanized, Chimeric and Human Antibothes Use for Treatment and Diagnosis Contemplated in the present invention is the use of murine, humanized, chimeric and human anti-AFF antibothes and fi-ments thereof in delivery methods of therapeutic and diagnostic/detection agents, and therieutic and diagnostic/detection methods. Preferably, the murine, chimeric, humanized and human anti-AFP antibothes and fiagments thereof are cbimeric, humamzed or human Immu31 antibothes. For example, a method of delivering a diagnostic/detection agent, a therapeutic agent, or a combintion thereof to a target comprising i) administering to a subject the antibody or fragment thereof an antibody, iiision protein, or frfment thereof; (ii) waiting a sufficient amount of time for an amount of the non-binding protein to clear the subject's blood stream; and (iii) admimsteriii to said subject a carrier molecule comprising a diagnostic/detection agent, a therapeutic agent, or a combination thereof, that binds to a binding site of SMd antibody. Preferably, the caixier molecule binds to m Tlie present invention also contemplates methods of diagnosing or detecting a malignancy in a subject. Diagnosis/detection may be accomplished by administering a diagnostically effective amount of a diagnostic/detection immimoconjugate, comprising an anti-AFP monoclonal antibody or frment thereof or a fiision protein or fragment thereof wherein said anti-AFP MAb or fragment thereof or fiision protein or fragment thereof is bound to at least one difostic/detection agent, formulated in a phamiaceutically acceptable excipient, and detecting said label. Preferably, the anti-AFP antibody, fusion protein, or fragment thereof is an Immu31 antibody. In a related vein, a method of diagnosing or detecting a maligiaiKy in a subject comprisii (i) performing aa in vitro diagnosis assay on a specimen from said subject with a composition comprising a anti-AFP MAb or fragment tfiseof or a antibody fusion iwotein or fragment thereof of any one of the antibothes, fu!sion jwoteins, or fragments thereof of the present invention, is also considered. Preferably, the in vitro diagnosis assay is selected from the group consisting of immunoassays, RT-PCR and immunohistochemistry. In the methods described herein, radioactive and non-radioactive ents can be used as diagnostic agents. A suitable non-radioactive dinostic ent is a contrast agent suitable for magnetic resonance imaging, a radiopaque gadolinium, complexed with metal-chelate combinations tiiat include 2-benzyl-DTPA and its nionomethyl and cyclohexyl analogs, wthen used along with the antibothes of the mvention. See U.S. Serial No. 09/921,290 filed on October 10,2001, w*uch is incoiporated in its entirely by reference. In a preferred embodiment, tiie contrast agent is an ultrasound-enhancing agent Still preferred, the ultrasound-«nhancing agent is a liposome. Radiopaque and contrast materials are used for enhancing X-rays and computed tomography, and include iodine compounds, barium compounds, gallium compounds, thallium compounds, etc. Specific compounds include bariimi, diatrizoate, etiiiodized oil, gallium citrate, iocarmic acid, iocetamic acid, iodamide, iodipamide, iodoxamic acid, iogulamide, iohexol, iopamidol, iopanoic acid, ioprocemic acid, iosefamic acid, ioseric acid, losulamide mumine, iosemetic acid, iotasul, iotetric acid, iothalamic acid, iotroxic acid, ioxelic acid, ioxotrizoic acid, ipodate, meglumine, metriiamide, metrizoate, prtyUodone, and tfaallous chloride. Also described in the present invention is the use of murine, chimmc, humanized and human anti-AFP antibothes and fi'agmraits thereof in methods for treating malignancies. For example, a malignancy of particuJar interest in tiiis patent is a cancer of the liver. Occasionally, ovarian carcinoma, and rarely gastrointestinal and lung cancers may produce AFP. Preferably, the anti-AFP antibothes and &agements thereof are Iinmu31 antibothes and fragments tiiereof. The me&od comprises administering to a subject a therapeutically effective amount of an antibody or fiagment thereof or an antibody fusion protein or fi'agment thereof comprising at least two MAbs or filaments thereof, wherein at least one anti-AFP MAb or fi-ment tiiereof or fusion protems or fragments thereof are any one of the antibothes of the present invention, formulated in a phannaceutically suitable excipient. In ano&er embodiment, a second MAb, &sion protein or ftagpiait thereof is not an anti-AFP antibody, fiision protein or fragment thereof In a related vein, a method of treating a cancer cell in a subject comprising (i) administering to smd subject a therapeutically effective amount of a composition comprising a naked or conjugated anti-AFP MAb or fragment thereof or antibody fusion protein or fragment thereof, of any one of the antibothes, fusion proteins, or fragments thereof of the present invention, (ii) formulating smd anti-AFP MAb or fiiagment thereof or antibody fusion protein or frment thweof in a phannaceutically suitable excipient, is contemplated. Preferably, such a composition fiather comprises a second antibody, fusion prtoein, or fragment thereof. The second antibody, fusion protein, or frment thereof may or may not be an anti-AFP antibody, fusion protein or firament thereof. Also preferred, the anti-AFP antibody, fusion protein, or fi-ment thereof is an Immu31 antibody, fusion protein, or figment thereof. The preferred mode of administration is parenteraily. Also preferred, the dosage is repeatedly administered. Still preferred, tiie anti-AFP antibody is administered in a dosage of 20 to 20W) milligrams protein per dose. The compositions for treatment contain at least one naked inuiine, humanized, chimeric or human anti- AFP antibody or figment thereof alone or in combination with other anti- AFP antibothes or antibody fragments thereof, such as other anti-AFP humanized, chimeric or himian antibothes. Preferably, the anti-AFP antibody, fusion protein, or fragment thereof in the composition for treatment is administered in a dosage of 20-2000 miligrams per dose. Also preferred, the and-AFP antibody or fragment thereof in the composition for treatment is an Immu31 antibody or fragment thereof The present invention also contemplates treatment with at least one naked hunwnized, chimeric or human anti- AFP antibody or fragment thereof in combination with other antibothes or antibody fragments thereof that are not anti-AFP antibothes, whereby these other antibothes can be administered unconjugated (naked) or conjugated with at least one diagnostic/detection or therapeutic agent For example, other antibothes suitable for combination therapy include, but are not limited to, carcinoma-associated antibothes and fragments thereof such as antibothes CEA, EGP-1, EGP-2 (e.g, 17-lA), MUC-1. MUC-2, MUC-3, MUC4, PAM-4, KC4, TAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, and Thomson-Friedenreich antigeis, tumor necroas antigCTis, tenascin, an oBcogene, an oncogene jaroduct, lL-6, IGF-1, IGFR-1, tumor angiogenesis antigens, such as vascular endothehum growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectin, and against other vascular growth factors, Ga 733, ferritin and acidic isoferritin (AIF) of primary hepatic carcinoma, or a combination thereof. Suitable antibothes could also include those targeted against oncogene markers or products, or antibothes against tumor- vasculature markers, siwh as the angiogenesis factor, VEGF, and antibothes against . certain immune response modulators, such as antibothes to CD40. Additionally, ,, treatment can be effected with at least one humanized, chimeric or human anti- AFP immunoconjugafe or fragment thereof alone or in combination witii anotiier anti- AFP antibothes or antibody fragments thereof, such as other anti- AFP humanized, chimfthc or human antibody. Preferably, the anti-AFP antibody is a fragment thereof is an Immu31 antibody or fragment thereof. Still preferred, compositions for treatment can contain at least one humanized, chimeric or human anti- AFP immunoconjugate or fragment thereof in combination with other antibothes or antibody fi:agments thereof that are not anti- AFP antibothes, these being eitiier ned or conjugated to a therapeutic agent Such non-anti-AFP antibothes Similarly, conjugated and naked anti- AFP humanized, chimoic or human antibothes or fi-agments thereof may be used alone or may be administered with, but unconjiated to, the various diagnostic/detection or therapeutic ents described herein. Also, naked or conjugated anti-AFP antibothes to the same or different epitope or antigen may be also combined with one or mote of the antibothes of the present invention. Preferably, tiie anti-AFP antibody or fragment flwreof is an lmmu31 antibody or fragment thereof. Accordingly, the present invention contemplates the administration of murine, humanized, chimeric and human Immu31 antibothes and fragments thereof alone, as a naked antibody, or administered as a mxiltimodal tiiery. Multimodal therapies of the present invention further include immunotherapy with naked or conjugated anti-AFP antibothes supplemented with admiruslration of other conjugated or unconjugated antibnody, fusion protein, or fragment thereof. For example, a humanized, chimeric or hmnan Immu31 antibody may be combined with another naked hinnanized, naked chimeric or naked human hnmu31 antibody, or a humanized, chimeric or human hnmu31 antibody immunoconjugate, such as a humanized, chimeric or human Immu31 antibody conjugated to an isotope, one or more themotherapeutic agents, cytoUmes, enzymes, enzyme-inhibitors, honnones or hormone antagonists, metals, toxins, or a combination thereof. A fusion protein of a murine, humanized, chimeric or human hnmu31 antibody and a toxin or may also be used in this invention. Many difiPerent antibody combinations may be constructed, either as naked antibothes or as partly naked and partly conjugated with a therapeutic agent or immunomodulator, or merely in combination with another therjeutic agents, such as a cytotoxic dmg or with radiation. The compositions for treatment contain at least one murine, humanized, chimeric or human monoclonal anti-AFP antibody or fragment tiiereof alone or in combination with other antibothes and fragments thereof such as other naked or conjugated, murine, faumanid, chimeric, or,human antibothes, or frments thereof or fiision proteins or fragments thereof, or tiierapeutic ents. In particular, combination therapy with a frilly human antibody is also contemplated and is produced by the mediods as set fortti above. Naked or conjugated antibothes, fiision proteins, or fragments thereof may be also combined with one or more of the antibothes, fiision (woteins, or fragraaits thereof to the same or difrerent epitope or antigen. For example, a naked, murine, humanized, chimeric or human Immu31 antibody may be combined with a nafced murine, humanized, naked chimeric or naked human Iinmu31 antibody; a muiine, humanized, chimeric or human naked lmmii31 antibody may be combined with a Imm»31 immuDOconjugate; a naked murine, humanized, diimeric, human Immxi31 antibody may be combined with a different antibody radioconjugate or a different naked antibody; a murine, humanized, chimeric or frdly human )inmu31 antibody may be combined with a murine, humanized, chimeric or human Immu31 antibody conjugated to an isotope, or to one or more chemothempeutic agents, cytokipes, toxins, enzymes, enzyme inhibitors, hormwies, honnone antionists, or a combination thereof. A fijsion protein of a murine, humanized, chimeric or human Immu31 antibody and a toxin or immunomodulator may also be used in this invention. Many different antibody combinations, targeting at least two dififerent antigens may be constructed, either as naked antibothes or as partly naked and partly conjugated with a tiierapeutic agent or immunomodulatoi, or merely in combination with another therapeutic agents, such as a cytotoxic drug or with radiation. Multimodal therapies of the present invention fiirther include immunotherapy with naked ImmuS 1 antibothes or fragments thereof supplemented with administration of carcinoma associated antibothes in the fonn of a conjugated or unconjugated antibody, fusion proteins, or fragment thereof. In a preferred embodiment, antibothes or fragments thereof for multimodal thery include, but are not limited to, antibothes against CEA, EGP-1, EGP-2 (e.g., 17-lA), MUC-1, MUC-2, MaC-3, MUCM, PAM-4, KC4, TAG-72. EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAN TD, and Tbomson-Friedenreicb antigens, tumor necrosis antiget tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, tumor aiogenesis antigens, such vascular endotheliuni growth factor (VEGV% placental growth fector (PIGF), EI>-B fibronectin, and other vascular growth factors, Ga 733, ferritin and acidic isofeiritin (AIF) of primary hqiatic carcinoma, or a combination thereof. These antibothes include polyclonal, monoclonal, chimeric, human or humanized antibothes and fragments thereof that recognize at least one epitope on these antigenic determinants. In another form of multimodal therqjy, subjects receive naked anti-AFP antibothes or fragments thereof and/or anti-AFP immunoconjugates or fra.gments thereof, in conjunction with standard cancer chemotherapy. Preferably, the anti-AFP antibody or fragment thereof is an Imniu31 antibody or fiment thereof. 5-fluorouracil in combination with folinic acid, alone or in combination with irinotecan (CPT-11), is a regimen used to treat colorectal cancer. Other suitable combination chemotherapeutic regimens are well known, such as with oxaliplatin alone, or in combination with ttiese other drugs, to those of skill in the art. In ovarian canoer, still a\bBt chemotherapeutic agents may be preferred, such as any one of the taxanes and platinum agents, Thio-TEPA and o&er alkylating agents (e.g., chlorambucil), as well as gemcitabine and other more recent classes of cytotoxic dns. In a preferred multimodal therapy, both chemotherapeutic drugs and cytokines are co-administered with a conjugated or unconjugated anti-AFP antibody, fiision protein, or frjmoit thereof accordmg to the present mvention. Preferably, the anti-AFP antibody or fragment thereof is an Immu31 antibody or fragment thereof. The cytokines, chemotherapeutic drugs and antibody, fusion protein, or fi:agment thereof can be administered in any order, or together. The present invention also encompasses the use of the bsAb and at least one therapeutic or diagnostic/detection agent associated with the linker moieties discussed above in intraoperative, intravascular, and endoscopic tumor and lesion detection, biopsy and therapy as described in U.S. Patent No. 6,096,289, and incorporated herein by reference. Preferably, the bispecific antibody has at least one arm that bimis the AFP antigen, and more preferably, the Imniu3I epitope. , ITie anti-AFP antibothes, fiision proteins, and fragments thereof of the prent tttvention can be employed not only for therapeutic or imaging purposes, but also as aids in porming research in vitro. For example, the bsAbs of the {Hsent invention can be used in vitro to ascertain if a targetable construct can form a stable complex with one or more bsAbs. Such an aay would aid the skilled artisan in idealising targetable constructs wiiich fonn stable complexes with bsAbs. "niis would, in turn, allow the skilled artisan to identify taig:etable constructs \ch are likely to be superior as therapeutic and/or imaging agents. Preferably, fee anti-AFP antibody, fusion protein, or fragment thereof is an ImmuSl antibody, fusion protein, or fragment thereof. The assay is advantageously performed by combining the targetable construct in question with at least two molar equivalents of a bsAb. Following incubation, the mixture is analyzed by size-exclusion HPLC to determine whether or not the construct has bound to the bsAb. Alternatively, the assay is performed usii standard combinatorial methods wherein solutions of various bsAbs are deposited in a standard 96-weil plate. To each well, is added solutions of targetable construct(s). Following incubation and analysis, one can readily determine which construct(s) bind(s) best to wiiich bsAb(s). It should be understood that tiie order of addition of tiie bsAb to the taietable construct is not crucial; that is, the bsAb may be added to the construct and vice versa Likewise, neither the bsAb nor the construct needs to be in solution; diat is, they may be added eitiier in solution or neat, wiiichever is most convenient Lasfly, the method of analysis for binding is not crucial as long as binding is established. Thus, one may analyze for binding using standard analytical methods iocluding, but not limited to. FABMS, high-field NMR or other appropriate method in conjunction wilh, or in place of size-exclusion HPLC. Bispecific Antibody TTterapy and Diagnosis The present invention provides a bispecific antibody or antibody fragment having at least one binding region that specifically binds a targeted cell marker and at least one other binding region that specifically binds a taigetable conjugate. The targetable conjugate comprises a carrier portion wiiich comprises or bears at least one epitope recognized by at least one binding region of the bispecific antibody or antibody fiagment For example, a method of treating or identifying diseased tissues in a subject, comprising: (A) administering to said subject a bi-specific antibody or antibody fragment having at least one arm that specifically binds a targeted tissue and at least one other arm that specifically binds a targetable conjugate, wherein said one aim tiiat specificially binds a targeted tissue is an Immi:31 antibody; (B) optionally, administering to said subject a clearing composition, and allowing-said composition to clear non-localized antibothes or antibody fiagments ftom circulation; (C) administering to said subject a first targetable conjugate which comprises a carrier portion which comprises or bears at least one epitope recogni2abie by said at least one other aim of said bi-specific antibody or antibody fi-agment, and one or more conjugated therapeutic or diagnostic agraits; and (D) en said therq)eutic agent is an enzyme, further administerii to said subject 1) a prodrug, when said enzyme is capable of converting said prodrug to a drug at the target site; or 2) a drug \lch is capable of being detoxified in said subject to form an intermediate of lower toxicity, when said enzyme is capable of reconverting said detoxified intermediate to a toxic fonn, and, therefore, of increasing the toxicity of said drug at the target site, or 3) a prodrug which is activated in said subject throng natural processes and is subject to detoxification by conversion to an intemiediate of lower toxicity, when said enzyme is capable of reconverting said detoxified intermediate to a toxic form, and, therefore, of increng the toxicity of said drug at the target site, or 4) a second tergetgfcble conjugate which comprises a carrier portion wiiich comprises orbears at least one epitope recognizable by said at least one other arm of said bi-specific antibody or -1 antibody fragment, and a prodrug, wben said enzyme is capable of convertii said prodrug to a drug at the target site, is described. Optionally, when said first targetable conjugate comprises a prodrug, administering a second targetable conjugate which comprises a carrier portion which comprises or bears at least one epitope recognizable by said at least one other arm of said bi-specific antibody or antibody or antibody fragment, and an enzyme capable of converting said prodn to a dn or of reconverting a detoxified intermediate of said drug to a toxic form. Preferably, the targetable conjugate comprises at least two HSG haptens. In a related vein, a method for detecting or treating tumors expressing AFP in a maxmnal is described. This method comprises (A) administerii an effective amount of a bispecifrc antibody or antibody fragment comprisii at least one arm diat specifically binds a targeted tissue and at least one other aim that specifically binds a targetable conjugate, wherein said one arm that specifically binds a targeted tissue is an hnmu31 antibody or frment thereof; and (B) administering a taietable conjugate selected from the group consisting of (i) DOTA-Phe-Lys(HSG)-D-Tyr-Lys(HSG>NH2; (ii) D0TA-Phe-Lys(HSG)-Tyr-Lys(HSG>NH2; (iii) Ac-Lys(HSG)D-Tyr-Lys(HSG)-Lys(Tscg-Cys)-NH2; optionally, fee method fiirther comprises admintsterii to a subject a clearing composition, and ailowing the composition to clear non-localized antibothes or antibody fragments from tlie circutatioa Bispecific antibothes and fragments thereof of the present invention are use&l in pretargeting methods and provide a preferred way to deUver two therapeutic %ents or two diagnostic/detection ients to a subject U.S. Serial No. 09/382,186 discloses a method of pretargeting using a biiediic antibody, in which the bispecific antibody is labeled with 'I and delivered to a subject, followed by a divalent peptide labeled with *c. TTie delivery results in excellent tumor/normal tissue ratios for 'l and *'c, thus showing the utility of two diagnostic radioisotopes. Any combination of imown therapeutic agents or diagnostic agents can be used to label the Inunu31 antibothes, lnunu31 fusion proteins, aiiul fragments thereof of the prraent invention. The bindii specificity of the Immu31 immunoconjiate, tiie efficacy of the thereutic agent or diagnostic agent and the effector activity of the Fc portion of the antibody can be determined by standard testing of tiie conjugates. The administration of a bsAb and & therapitic agent aociated with &e linker moieties discussed above may be conducted by administering the bsAb at some time prior to administration of the therapeutic agent which is associated with the linker moiety. The doses and timing of the rejents can be readily devised by a skilled artisan, and are dependent on the specific nature of the reagents employed. If a bsAb-F(ab'>i derivative is ven first, then a waiting time of 24-72 hr before administration of the linker moiety would be appropriate. If an IgG-Fab' bsAb conjugate is ihe primary targeting vector, then a longer waitii period before administration of the liiUcer moiety would be indicated, in the range of 3-10 days. After sufficient time has passed for tfie bsAb to target to the diseased tissue, the diagnostic/detection agent is administered. Subsequent to administrationof the diagnostic/detection agent, imaging can be performed. Tumors can be detected ih body cavities by means of directly or indirectly viewii: various strwtures to which energy of the q)propriate wavelength is delivered and then collected. Lesicwis at any body site can be viewed so long as nonioni2ing radiation or energy can be delivered and recaptured &om these structures. For example, PET which is a hi resolution, non-invasive, imjing technique can be used with flw inventive antibothes for the visualization of human disease. In PET, 511 keV gamma photons produced during positron annihilation decay are detected. The linker moiety may also be conjugated to an «izyme c;mble of activatii a prodrug at the target site or improving the efficacy of a normal thea-apeutic by controUmg the body's detoxification pathway. Following administration of tiie bsAb, an enzyme conjugated to the linker moiety, a low MW hapten recognized by the second arm of dte bsAb, is administered. After the enzyme is pretareted to the target site, a cytotoxic drug is injected, which is known to act at tiie tar site. Tlie drug may be one Ach is detoxified by the mammal's ordinary detoxification processes. For example, the drug may be converted into the potentially less toxic glucuronide in the liver. The detoxified intermediate can then be reconverted to its more toxic form by the pretargeted enzyme at the target site. Alternatively, an administered prodrug can be converted to an active dmg by the pretargeted tmzyme. The pretargeted enzyme improves the efficacy of the treatment fay Kcycling the detoxified dn. This approach can be adopted for use with any enzyme-dn pair. The enzyme capable of activating a prodmg at the target site or improvir the efScy of a normal therapeutic by controlling the body's detoxification pathways may atematively be conjugated to the hapten. The enzyme-hapten conjugate is administered to the subject following administron of the pre-tar-getii bsAb and is directed to the target site. After the enzyme is localized at the target site, a cytotoxic drug is injected, wluch is known to act at the target site, or a prodrug fonn thereof which is converted to the drug in situ by the pretargeted enzyme. As discuss above, the drug is one \NWch is detoxified to form an intermediate of lower toxicity, most commonly a glucuronide, using tiie mammal's ordinary detoxification processes. The detoxified intermediate, e.g., the glucuronide, is reconverted to its more toxic form by the pretargeted enzyme and thus has enhanced cytotoxicity at the target site. This results in a recycling of the drug. Similarly, an administered prodrug can be converted to an active drug tiirough normal biological processess. The pretargeted eazymc improves the efficacy of the treatment by recycling the detoxified dn:. This approach can be adopted for use with any enzyme-drug pair. The invention further contemplates the use of &e inventive bsAb and the diagnostic agent(s) in the contort of Boron Neutron Capture Thery (BNCT) protocols. BNCT is a bmary system designed to deliver ionizii] radiation to tumor cells by neutron irradiation of tumor-localized ' atoms. BNCT is based on the nuclear reaction which occurs vAisa a stable isotope, isotopically rairiched '**B (present in 19.8% natural abundance), is irradiated with thermal neutrons to produce an alpha particle and a Li nucleus. These particles have a path lengdi of about one cell diameter, resulting in high linear energy transfer. Just a few of the short-raie 1.7 MeV alpha particles produced in this nuclear reaction are sufficient to target the cell nucleus and destroy it. Success with BNCT of cancer requires methods for localig a high concentmtion of " at tumor sites, diile leaving non-target organs essentially boron-fiee. Compositions and mediods for treating tumors in.subjects using pre-targeting bsAb for BNCT are described in co-pending Patent Appl. Serial No. 09/205,243, mcoiporated herein in its entirety and can easily be modified for the purposes of the present invention. A clearing agent may be used w4uch is given between doses of the bsAb and the linker moiety. Tlie present inventors have discovered that a clearing agent of novel mechanistic action may be used with the invention, namely a glycosylated anti-idiotypic (anti-Id) Fab' fragment targeted against the disease targeting arm(s) of tiie bsAb. For example, anti-CSAp (Mu-9 Ab) x auti-peptide bsAb is given and allowed to accrete in disease targets to its maximum extent To clear residual bsAb, an anti- idiotic (anti-Id) Ab to Mu-9 is given, preferably as a glycosylated Fab' fragment The clearing agent binds to the bsAb in a monovalent manner, wbile its appended glycosyl residues direct the entire complex to the liver, where rapid metabolism takes place. Then the therapeutic which is associated with the linker moiety is given to the subject The anti-Id Ab to the Mu-9 ami of the bsAb has a hi athnity and the clearance mechanism differs from otha: disclosed m«;hanisnB (see Goodwin et al., ibid), as it does not involve cross-linking, because the anti-Id-Fab' is a monovalent moiety. AJso contemplated herein is a kit useiiil for treating or identifying diseased tissues in a subject comprising: (A) a bi-specific antibody or antibody fragment having at least one arm that specifically binds a taigeted tissue and at least one other ami that specifically binds a targetable conjugate, wherein said one arm that specifically binds a targeted tissue is an Immu31 antUjody or franent thereof; A method of screeing for a targetable conjugate is also described, comprising (A) contacting said targetable construct with a bi-specific antibody or antibody fragment having at least one ann tiiat speciiicaUy binds a targeted tissue and at least one other arm that specifically binds said targetable conjiate to give a mixtiire, wherein said one arm that specifically binds a targeted tissue is a Inunu31 anUbody or fragment thereof; and (B) optionally incubating said mixture; and (C) analyzing said mixture. The present invention further provides a method for inuring malignant tissue or cells in a mammal expressing AFP; a method of intraoperatively identifying/disclosii diseased tissues expressing AFP, in a subject; a method for endoscopic identification of diseased tissues expressing AFP, in a subject and a mediod for the intravascidar identification of diseased tissues expressing AFP, in a subject Such methods comprise (A) administering an effective amount of a bispecific antibody or antibody fragment comprising at jeast one arm that specifically binds a targeted tissue expressing AFP and at least one other arm that S5)ecificaUy binds a targetable conjugate, wherein said one arm that )ecificaUy binds a targeted tissue is an ImmuSl antibody or firagment thereof, ai (B) administering a taigetable conjugate selected &om the group consisting of (i) iX>TA-Hie-Lys(HSG)-D-Tyr-Lys(HSG)-NH2; (iiO D0TA-Phe-Lys(HSG)-Tyr-tys(HSG)-NH2; Also considered herein is a method of detection of lesions durii an endoscopic, laparoscojac, intravascular cathetcj, or suical procedure, vthereiufce method comprises: (A) injecting a subject v/bo is to imdeago such a procedure with a bispecific antibody F(ab>2 or F(ab')2 fiagment, whn the bispecific antibody or fragment has a first antibody binding site which specifically bmds to a AFP antigen, and has a second antibody binding site which specifically binds to a hapten, and permitting the antibody fiagraent to accrete at target sites; (B) optionally clearing non-taeted antibody fiagraents using a galactosylated anti-idioQ-pe clearii agent if tire bigsecdfic fragment is not largely cleared from circulation within about 24 hours of injection, and injecting a bivalent labeled hapten, vAuch quickly localizes at the taiget site and clears tiirou the kidneys; (C) detecting the presaice of the hapten by close-raie detectiMi of elevated levels of accreted label at the target sites with detection means, within 48 hours of tite first iiection, and conducting said procedwe, Wher said detectioQ is performed without the use of a contrast agent or subtraction £ent Preferably, the hten is labeled vnih a diagnostic/detection radioisotope, a MRl ime-enhancing agent or a fluorescent label. hi a related vein, a method for close-raie lesion detection, durii an operative, intravascular, laparoscopic, or endoscopic procedure, wherein the method comprises: (A) injectii a subject to such a procedure parenterally with an effective amount of an Immu31 immunoconjugate or fragment thereof, (B) conductii the procedure within 48 hours of the injection; (C) scanning the accessed interior of the subject at close range with a detection means for detecting the jHsence of said labeled antibody or fragment thereof; and (D) locating the sites of accretion of said labeled antibody or fiagoient thereof by detecting elevated levels of said labeled antibody or fr'ment thereof at such sites with the detection means, is also described. 9. Phannacentically Suitable Excipients The murine, humanized, chimeric and human Immu31 MAbs to be delivered to a subject can consist of the MAb alone, inununocoiyugate, fiision protein, or can comprise one or more pharmaceutically suitable excipients, one or more additional ingrethents, or some combination of these. The conjugated or unconjugated anti-AFP antibothes and fi'agments theteoC or fusion proteins and fragments thereof of the present iaventiont:an be formulated according to known methods to prepare pharmaceutically useful compositions. Preferably, the anti-AFP antibody or fragment thereof is an Immu31 antibody or fragment thereof. Sterile phohate-buffered salme is one exarcle of a pharmaceutically suitable excipient Other suitable excipients are well-known to those in the art. Sec, for example, Ansel et al, PHARMACEUTICAL DOSAGE FORMS AND DRUG DELIVERY SYSTEMS, 5th Edition (Lea & Febiger 1990), and Gennaro (ed.), REMINGTON'S PHARMACEimCAL SCIENCES, 18th Edition (Mack Publishing Company 1990), and revised editions thereof. The conjugated or unconjugated anti-AFP antibody, fusion protein, or ftagtoents thereof of the present invention can be fonnuJated for intravenous adnunistration via, for example, bolus injection or c Additional phamiaceutical methods may be employed to control the duition of action of the therapeutic or dmostic/detection immunoconjugate or mksd antibody, ftision protein, or fragments thereof. Control release preparatioDS can be prepared through the use of polymers to complex or adsorb the immunoconjugate or naked antibody. For example, biocompatible polymers include matrices of poly(ethyIene-co-vinyl acetate) and matrices of apolyanhydridecopolymerofa stearic acid dimer and sebacic acid. Sherwood et al, Bio/Technology 10:1446 (1992). The rate of release of an immunoconjugate or antibody from such a matrix depends upon the molecular weight of the immunoconjugate or antibody, the amount of immunoconjugate, antibody wiUiin the matrix, and ihs. size oftlispersed particles. Salizinaaet ai, Biophys. J. 55:163 (19B9); Sherwood etal., supra. Other solid dosage forms are described in Ansel et al., PHARMACEUTICAL DOSAGE FORMS AND DRUG DELIVERY SYSTEMS, 5th Edition-(Lea & Febiger 1990), and Gennaro (ed.), REMINGTON'S PHARMACEUTICAL SCIENCES, 18th Edition (Mack Publishing Company 1990), and revised editioia thereof. The conjugated or unconjugated anti-AFP antibody, fiision protein, or fragments thereof may also be administered to a mammal subcutaneously or even by other parenteral routes. Moreover, the administration may be by continuous inlfion OT by single or midtiple boluses. Bi general, the doge of an administered immunoconjugate, or naked antibody, iusion protein or fragments thereof for humans will vary depending upon sudi factors as the patient's age, weit, height, sex, general medical condition and previous medical history. Typically, it is desirable to provide the recipient with a dosage of immunoconjugate, naked antibody fusion protein, naked antibody, or fragments thereof that is in the raie of from about Img/kg to 20 mg/kg as a siie intravenous infrisioo, although a lower or higher, dosage also may be administered as circiunstances dictate. Tliis dosage may be repeated as needed, for example, once per week for 4-10 weeks, preferably once per week for 8 weeks, and more preferably, once per week for 4 weeks. It may also be given less frequently, such as every other week for several months. The dosfe may be given through various parenteral routes, with propriate adjustment of dose and schedule. For putxx>ses of therapy, the conjugated or unconjiated antibody, fusion protein, or fragment thereof is administered to a mammal in a therapeutically effective amount. Preferably, the anti-AFP antibody or frfment thereof is an Immu31 antibody or fragment thereof. A suitable subject for the present invention is usually a human, although a non-human animal subject is also contemplated. An antibody preparation is said to be administered in a "therapeutically effective amount" if the amount administered is physiologically significant An agent is physiologically significant if its presence results in a detectable change in the physiology of a recipient mammal. In particular, an antibody preparation of the present invention is physiologically significant if its presence invokes an antitumor response or mitigates the signs and symptoms of an autoimmune disease state. A physiologically significant effect could also be the evocation of a humoral and/or cellular immune response in the recipient manunal. 10. Expression Vectors The DNA sequence encodit a murine, humanized, chimeric or human Immu31 MAb can be recombinantly engineered into a variety of known host vectors that provide for replication of the nucleic acid. These vectors can be designed, using known methods, to contain the elements necessary for directing transcription, translation, or both, of the nucleic acid in a cell to which it is delivered. Known methodology can be used to generate expression constructs tibe have a protein-codii sequence operably linked with appropriate traoscriptional/translational control siials. These methods include in vitro recombinant DNA techniques and synthetic techniques. For example, see Sambrooke/a/., 1989, MOLECULAR CLONING: A LABORATORY MANUAL. Cold Spring Harbor Laboratory (New Yoric); Ausubel et al. 1997, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons (New Yoric). Also provided for in this invention is Ihe delivery of a polynucleotide not associated wiUi a vector. Vectors suitable for use in the instant invention can be viral or non-viral. Particular examples of viral vectors include adenovirus, AAV, herpes simplex virus, lentivirus, and retro\irus vectors. An example of a non-viral vector is a plasmid. In a preferred embodiment, the vector is a plasmid. An expresaon vector, as described hendn, is a polynucleotide comprising agene that is expressed in a host cell. Typically, gene expression is plac»l luder the control of certain regulatory elements, includii constitutive or indwle i»r(»noteis, tsufrpoaSe regulatory elemeate, and enlrancCTs. Such a gene h said to be "operably linked to" the regulatory elements. Prefeably, the ejression vector of the instant invention comprises the DNA sequoKe encoding a humanized, chimeric or human htunu31 MAfa, which includes both the heavy and the light chain variable and constant regions. However, two expression vectors may be used, with one comprising the tieavy chain variable and constant regions and the other comprising the light chain variable and constant regions. Still preferred, the expression vector fiirther comprises a promoter, a DNA sequence encoding a secretion signal peptide, a genomic sequence encodii a human Ig light or heavy chain constant region, an Ig enhancer element and at least one IMA. sequence encoding a selection marker. * * * The invention is fiirther described by reference to the following examples, which are provided for illustration only. The invention is not limited to the examples but rather includes all variations that are evident fiom tfie teachings provided herein. EXAMPLES Example 1. Molecular Cloning and Sequence Elucidation for Immu31 Heavy and Light Chain Variable Regions The VH and VK genes of ImmuS 1 was obtained by RT-PCR as described by Orlandi et al. (PNAS 86:3833-3837 (1989) and Uung et al. (Hybridoma 13:469-476 (1994). The total RNA was prepared from Inunu31 hybridoma cells and RT-PCR was perfbnned to isolate the V genes as described (Leung et al. Hybridoma 13:469-476 (1994)). Briefly, the first strand cDNA was reverse transcribed from total RNA using the Superscript preamplification system (GIBCO/BRL) in a reaction volmne of 60 [il containii 20 g of the RNAs annealed with 150 ng of random hexamer primer, 20 mM Tris-HCl. pH 8.4,15 mM KCl, 2.5 mM MgCIi. 5 mM dNTP mix, 10 mM DTT, 0.1 mg/ml BSA, and 600 units of Superscript reverse tmascriptase. Hie elongation step was initially allowed to proceed at room temperature for 10 min followed by incubation at 42*'C for 50 rain. The reaction was terminated by heating the reaction mixture at 90C for 5 min. PCR reactions using the first strand cDNA as templates were then carried out to amplify mouse Ig VH and VD genes. The VD sequence of Immu31 was amplified by using the primer pair VKIBACK (Orlandi et al. PNAS 86:3833-3837 (1989) CK3'-BH (Leung et al. (Leung et al., 1993)). Tlie resulting PCR products were -350 bp. While the VH sequence was amplified with VHIBACK (Orlandi et al. PNAS 86:3833-3837 (1989)) and CHl-C (5'-AGCTGGGAAGGTGTGCAC-3'), which anneals to the CHI region of mupne y chains, resulting in PCR products of-500 bp. Both Vk and VH PCR fragments were cloned into pCR2.1 AT-cloning vector and the DNA sequences were determined by DNA sequencing (Sanger et al. PNAS 74:5463-5467 (1974)). Multiple clones (8 for each) were selected for sequencii to eliminate possible errors resulted fix>m PCR reaction. Majority of clones contained an identical murine Ig VH (6) or VK (7) sequence, which was designated as Immu31VH and IramuSlVic, respectively (Figure 1). Tlie amino acid sequences encoded by the genes were deduced and are also shown in Figure 1. No defective mutations were identified within the sequences and important residues such as cycteines for inlradomain disulfide linkies were located at appropriate positions. Conqjarison witii other mouse VK sequences revealed that Immu31 VK is a member of the kaj light chain subclass V while Immu31VH belongs to mouse Ig heavy chmn subclass HA (Kabat et al., 1991). Example 2. Construction of the expression vector for a chimeric Immii31 To evaluate the "authenticity" of the cloned V gene senents, the putative murine \D and VH W«B constructed into a chuneric IrnmuBl (clmmuSl) containing humaa IgG and kappa constant donmins and expressed in SfO cells. To cilitate subcloning of Immu3lVK (Figure 1 A) to generate the expiession vector, the DNA sequence vras modified at 3'end to include a Bglll restriction site, AGATCT, by PCR amplification with primers VKIBACK and VKIFOR (Orlandi et al. PNAS 86:3833-3837 (1989)). The resulting PCR product vias digested with PvuH and BglH and force-cloned into a pBR327-based staging vector (dested vnth PvuII imd BclT), VKpBR, vAich contained Ig promoter, signal peptide sequence for secietion and convenient restriction sites to fecilitate in-fiame ligation of fee VK PCR product (Leung et al.(Leung et al., 1994)). Similarly, tive nucleotide sequences at positions 336-342 of hImmu31VH (Figure IB) were converted to BstEH site, GGTCACC, by PCR with primers VHIBACK and VHIFOR (Orlandi et al., 1989). The VH PCR product was then digested with PstI and BstEH and lated into PstI and BstEU digested VHpBS, a pBluescript-based staging vector containing an Ig promoter, a signal peptide sequence and ccmvenirait restriction sites for in-firame-ligation of a VH sequence. The final V sequences in the clmmuS 1 were designated as clmmu31 VH and VK; confimied by DNA sequencing and shown in Figure 2A and 2B, respectively. The fiagments containing the VH and VK sequences of clmmu31, together with the promoter and signal peptide sequences, were excised fixtm the respective staging vectors, clmmu31 VHpBS and clmmu31 VKpBR, by double liestriction-digestion vrith Hmdlll and BamHI. The ca. 850 bp VH fragment was then subcloned into the HindHI/BamHI site of a mammalian expression vector, pGlg, in wch clmmu31 VH was linked to the genomic sequence of the human y I constant gene (Leung et al.(Leung et al., 1994)). Similarly, the ca. 650 bp VK fragment was incited into the HiudlH/BamHI site of pKh, which carrying theenomic gene-sequence of a human K constant region, an Ig enhancer, a K enhancer, and the hygromycin-resistant gene as a marker for selection of transfectants (Leung et al.Qung et al., 1994)). The final expression vectors were desigimted as chnmu31pGlg and chnmu31pKh, respectively. Example 3. Transfection and expression of chimeric and humanized ImmuSl Same procedures were employed to express clmmu31 or hlmmu31 in Sp2/0 cells by transfection as described by Leung et al. (Hybridoma 13:469-476 (1994)). As an example, expression of clnunu31 described here. Briefly, linearized clnunuS IpKh and clmmu3 IpG I g were co-transfected into Sp2/0 cells by electroporation. Ihe transfected cells were grown in 96-well plate for 2 days and then selected by the addition of hygromycin at a final concentration of 500 units/ml. The colonies began to emerge 10-14 days after electroporation. Siqiematants fit>m colonies sinivii selection were screened for the presence of mouse-human chimeric IgG by ELISA. Briefly, supernatant samples &om surviving clones were added in triplicate to ELISA microtiter plates precoated with goat anti-human (GAH) feG, F(ab')2 fragment-specifc antibody (Jackson ImmunoResearcfa, West Grove, PA). The plates were incubated for 1 h at room temperature. Unbound proteins were removed by washing three times witii washing buffer (PBS with 0.05% poIysorbate-20). Horseradish peroxidase -(HRPxjnjugated GAH IgG, Fc fragment-specific antibody (Jackson ImmunoResearch) was then added to the wells. Following incubation for 1 h, the plates were washed six times with washing bu£fer. A substrate solution contaming 4 mM of o-pbenylenediamme dihydrochloride (OPD) and 0.04% HaC, v added to the wells. The reaction was allowed to proceed in the dark for 30 min and stopped by the addition of H2SO4 solution into each well before measuring absorbance at 490 nm in an automated ELISA reader. The positive cell clones were expanded and clmmu31 was purified from cell culbffe supOToatant by affinity chromatograpgy on a Protein A column. A competition Ag-binding assay wasT:attried out to compare the inmiunoreactivity of chimeric and murine Immu31 Example 4). As shown in Fig. 3, clmmu31 and murine Immu31 competed equally well for the binding of biotinylated murine ImmuSl to the AFP antigen. These data demonstrated that the immunoreactivi of clinrau31 is comparable to that of murine hnmu31, tbus codfinuing the authenticity of the VD and VH sequence oUainai (Fig. 1). Similar procedures were also used with another expression vector, pdHL2, as described in Example 5. Approximately 30 ng of hItnmii31pdHL2 was linerized by digestion with Sail and transfected into Sp2/0 cells by electroporadon. The transfected cells were plated into 96-weU plate wd were allowed to recover for 2' days. After two days, MTX at a final concentration of 0.025 Q M was added to tiie medium to select transfectants. MTX-resistant clones emeiged in 2 weeks and Supematants &om colonies sur\ving selection wa% monitored for human IgG secretion by ELISA as described above. Positive cell clones were expanded and hlnunu31 was purified from cell culture supernatant by afBnity chromatognqjgy on a Protein A column. Example 4. The Ag-binding activify assays The Ag-binding activities of clmmu31 and hhnmu31 wo-e detennined with ELISA in ELISA microplate wells coated with AFP (Scripps Research fastitute. La JoIIa, CA). Briefly, constant amoimt of biotinylated murine Immu31 was mixed with varying concentrations (0.01-100 Dg/ml) of testing Abs (Immu3I, clmmii31 or hhnmu31), and added into AFP-coated microwells, and incubated at room temperature for 1 h. After washing, HRP conjugated streptavidin was added and incubated for 1 h at room temperature. The amount of HRP-conjugated streptavidin bound to the AFP-bound biotinylated Immu3! was revealed by reading OD at 490 nm in an ELISA reader after the addition of a substrate solution containing 4 mM OPD and 0.04% H2O2. Example 5. Choice of human frameworks and sequence design for hlmmuSl By comparii the murine lmrau31 V region PR sequences to that of hunmn Abs in the Kabat database (Sequences of Proteins of Immunological Interest (Bethesda, MD: U.S. Departmet of Health and Human Services, Public Health Service, National Institute of Health, 1991), the FRs of human REI and EU VH were foimd to exhibit the highest degree of sequence homology to that of Immu31VO and Immu31VH, respectively (Fig. 4). One exception is the FR4 of Immu31\, which showed the highest sequence homology with that of NEWM VH (Fig. 4A). Thus, the FR sequences of REl VD (Fig. 4B), FRl-3 of EU VH and FR4 of NEWM VH (Fig. 4A) were selected as the scaffold for grafting the respective CDRs of hmnu31. A few amino acid residues in murine FRs that flank the putative CDRs were maintained in hhnmu31 based on the consideration that these residues have more impact on Ag binding than other FR residues. These residues are 5Q, 27Y, 28A, 30T, 46Y, 481, 66K, 67A and 94R of VH, and 4L, 39K, 48M, 49H, 581,69R, lOOG and 107K of YD. Additionally, based on the results of previous humanization of LL2 (Leung et al. Mol. hnmunoh 32:1413-1427 (1995)), two charged residues, 39K in FR2 and 69R m FR3 of hnmu31V D, that have the potential of CDR contacts and might affect the immimoreacdvi of the resultant Ab were retained in the design of the humanized FR sequences (Fig. 4B). In order to evaluate the impact of the charged murine residues 39K and 69R on &e binding activity of the Ab, two alternate versions of humanized VD, hInunu31VKT39, and hInnmu31VKT69, were designed by substituting either residue 39K or 69R with the corresponding human residue, threonine, respectively (Fig.4C). Figures 3A compares the VH sequence of human EU with murine and hirnianized Inmiu31 VH, and 3B compares human REI with murine and humanized Immu31 Vn. The dots indicate the residues in Inunu31 and hlmmu31 sequences that are identical to the correspond!] residues in the human VH and VD sequences. Figure 3C shows the difference between hhnmu31VD and two variants, . Wmmu3IVDT69 and hlmmu3IVDT39. The DNA and amino acid sequences of hlmmu31 VH and VD are shown in Figure 5A and 5B, respectively. Example 6. Expression and characterization of hlmmu31 The strategy as described by Leung et al. (Leung et al., 1994) was used to construct the designed V D and VH genes for hlmmu31 usu a combination of long oligonucleotide systheses and PCR. Each variable chain was constructed in two parts, a 5'- and 3'-half, designated as "A" and "B" respectively. Each half was produced by PCR amplification of a single strand synthetic oligonucleotide template with two short flanking primers, using Taq polymerase. The amplified Segments were first cloned into the pCR2.1 TA cloning vector from Invitrten (Cailsbad, CA) and subjected to DNA sequencing. The templates and primer pairs are listed as follows: Template Primers hImmu31VHA VHBACKATJa hImmu3IVHB VHbA'HFOR hImmu31VKA VKBACK/VKa hImmu3IVKB VKbAKFOR' hlmmu31VH domain For the construction of the hlmmu31 VH domain, two loi oligonucleotides, hImmu3IVHA (135-mer) and hImmxi31VHB (151-mer) were synthesized on an automated DNA synthesizer (Applied Biosystem). The sequence of loi oligo HmmuSlVHA represents the minus strand of the hhnmu31VH domain complementary to nt 28 to 162andthatofhhnmu3]VHB was complement to nt 181-331 as listed below. hhnmu31VHA(135bp) 5'-GTAAGGATGA ATATATCCAA TCCAATACAG ACCCTGTCCA GGTGCCTGCC TGACCCAGTG TATAACATAG CTAGTAAAAG CGTAGCCAGA AGCCTTGCAG GAGACCTTCA CTGATGACCC AGGTITCTTG ACTTC-3' hhmnu31VHB(151bp) 5'-CTTGGCCCCAGTAAGCAAAA GGGTCTCCCC CCCCAGATCT TGCACAAAAA TAAAATGCCG TGTCCTCAGA CCTCAGGCTG CTCAGCTCCA TGTAGGCTGT ATTGGTGGAT TCGTCAGCTG TTATTGTGGC CTTGCCnTG AACTTCTCAT T-3' hhrunuBlVHA was amplified by PCR with a pair of primers VHBACK and VHa, while hImmu31VHB was amplified with VHb and VHFOR. The sequences of these primers are hsted below: VHBACK 5'-CAGCTGCAGC AATCAGGGGC TGAAGTCAAG AAACCTG-3' VHa 5'-GTACTTGGTA CCACCATTGT AAGGATGAAT ATATCC-3' VHb S'-AATGGTGGTA CCAAGTACAA TGAGAAGTTC AAAGGC-3' VHFOR 5-'GGAGACGGTG ACCAGGGAGC CTrGGCCCCA GTAAGC-3' vfbeTC underlined sequences represent the restriction sites, Psd, Kpnl, Kpi and BstEn, respectively. The resultii double-stranded PCR product VHA and VHB, were digested with Pstl/Kpnl and KpnI/BstEII, respectively, gel purified, a assembled into the Pstl/BstEII sites of the heavy «hain staging vector, VHpBS, forming the fiiU length hlmmu31VH gene (Figure 5A). "ITie humanized A'H sequi was subcloned into the pGlg vector, and the resultant human IgGl heavy chain expression vector was designated as hlmmu3 IpGlg. hlmmuSlVO domain Similarly, for the construction of hlnimu3 IVD domain, long oligonucleoti hhrunuSl VKA and hlmmuSl VKB were used as template to construct the VQ ges Wmmu3IVKA represents the minus strand of the hImmu31VQ domain complementary to nt 23 to 13 5 and that of Wmmu31VKB was complementary to i 155-306 of the designed hImmu31Va (Figure 5B). hhnmu31VKA(n3bp) 5'-TTTAGGTGCT ITCCCTGGTr TCTGCTGGTA CCAACCTATA TACTTGrrAA TGTCTTGGCT TGCCTTACAA GTGATAGTGA CCCTATCTCC AACAGATGCG CTCAGAGATG ATG-3' hImmu31VKB(152bp) 5'- CTTGGTCCCT CCACCGAACG TCCACAGATC ATCATACTGT AGACAATAAT ATGTTGCAAT GTCTTCTGGT TGAAGAGAGC TGATGGTGAA AGTATAATCT GTCCCAGATC CGCTGCCAGA GAATCGCGAA GGGATACCTG GCAGTAATGC AG-3' hlmmuGlVKA was PCR-amplified with ttie primer pair of VKBACK and VKa, while hlimnu31VKB was amplified with VKb and VKFOR. The sequences of these primers are listed below: VKBACK 5 '-GAC ATT CAGCTG ACC CAG TCT CCA TCA TCTCTGAGCGC-3' VKa 5'-A TGT GTA ATGCAT CAG CAG TTT AGG TGC TTT CC-3' VKb 5'-CTG CTG ATG CAT TAC ACA TCT GCA TTA CTG CCA GG-3' VKFOR 5'-GA CCG GCA GAT CTG CAG CTT GGT CCC TCCAC-3' The underUned sequences in VKBACK, VKa, VKb, and VKFOR repjsent PvuII, Nsil, Nsil and BgUI restriction sites, respectively. The resulting double-stranded PCR products, VKA and VKB, were digested with PvuII/Nsil and Nsil/Bgin, respectively, gel purified, and assembled into the PvuH/BclI sites of the light chain stagmg vector, VKpBR. Finally, the humanized VD sequence was subcloned into the light chain expression vector, pKb, forming hImmu31pKh. liImmu31VDT39 andhImmii3IVaT69 were similarly constructed and the final expression vectors for these two variants were hlmmu3 IT39pKh and hlmmu31 T69pKh, respectively. Hie final expression vector far hlatmu31 Using the two-expression vector system described above, i.e. pGlg and pKh, is preferred in the initial stage of humanization because it provides flexibility of testing various combinations of VK and VH constructs. Tlie defective designs, if any, residing in the individual heavy or light chain can be systematically identified and corrected by mixing and matching each of the humanized chains with their chimeric partners. However, the transfccted cells generated from the pGIg/pKh system typically produce antibothes at a level of less than 1 mg/Iiter of terminal culture. To generate high-level antibody-producing eel! lines, a single expression vector, pdHL2, is preferred for the production of hlmmuS 1. pdHL2 contains the expression casettes for both human IgG heavy and lit chdi under the control of IgH enhancer and MTi promoter, as well as a mouse dhfr gene, controlled by a weak S V40 promoter, as a maiter for selection of transfectants and co-amplification of the trans-genes (Gjllies et aL,y. Immunol Methods 125:191 (1989); Losman et al.. Cancer 80:2660 (1997)). By replacing the VK and VH segments of pdHL2, different chimeric or humanized Abs can be eiqrressed. To construct the pdHL2 expression vector for hlmmu31, hlnunu31 VH and VDgene segments were subcloned into another set of staging vectors, VHpBS2 and VKpBR2, respectively. VHpBS2 is a modified staging vector of VHpBS (Leung et al., Hybridoma, 13:469 (1994)), into which a Xhol restriction site was introduced at 16 bases upstream of the translation initiation codon. Similariy, VKpBR2 is a modified staging vector of VKpBR (Leung et al., Hybridoma, 13:469 (1994)), mto \rfiich a Xbal restriction site was introduced at 14 bases upstream of the translation initiation codon. The final expression vector hlmmu3 IpdHL2 was constructed by sequencially subcloning the Xbal-BamHI and XhoI/BamHI fiagments of hlmmu31 Vk and VH, respectively, into pdHL2. The final eiqiression vector was designated as hImu31pdHL2. Ejqjression and binding activity assays/or hlnwmSl The methods for transfection, screening positive transfected clones and bindii activity assays for hlmmu31 were same as described for clmmuS 1 (see Example 3). Three versions of the humanized Ab, hlmmu31, hInunu31T39 and hImmii3lT69, were expressed in Sp2/0 cells by co-tiansfection of the heavy chain expression vector, hlmmu3 IpGl g, with either of the kappa chain expression vectors: Mmmu3 IpKb, WmmuS 1T3 9pKh or hlmmu31 T69pKh. The Ag-binding activities of these humanized Abs were evaluated by the same competitive bindii assay. While the AFP binding affinity of hlmrau31 and hImmu31T69 was similar to that of murine IrnniuS 1 or clniimi31, judging from their comparable competition with bJotin-ImmuSl (Fig. 6A),hInimu31T39 was somewdiat inferior (Fig. 6B). These results demonstrated tiie successfiil humanization of Inmiu31 and revealed that the murine kappa diain FR residue K but not R is important for maintaining the immimoreactivify of Immu31. The typical productivity of Abs from transfected Sp2/0 cells by usii% pKh and pGlg oqiression vector system is in the single digit raie of nulligram per liter, vAikh is practically insufficient for production of lae quantities of Abs for ctinical plications. In &e case of hlmmtiS 1, the highest productivity of selected clone co-transfected withhImmu31pKhandhImmu31pGlgwas2-3mg/L. To increase the capability of the transfected cells to produce hlmmu31, the heavy and kappa chain repression cassettes were re-constructed into one single expression vector, pdHL2, -ftch contains the murine tHiJr gene and allows for subsequent amjification of the transfected gene products with stepwise increase of MTX concentrations. Three hImmu31pdHL2 transfected clones, 314.2C11, 322.1(34 and 323.2H2, tbat were initially selected with 25 nM MTX and estimated to be producing 4,15 and 8 mg/L of blmmu31, respectively, were subjected to amplification using procedures as described by Losman et al. (Cancer 80:2660 (1997)). As the MTXiconcentratiOTi in the cell culture medium gradually increased from 0.1 to 3 QM, tiie productivity of falmmu31 from these cells was increased concomitantly and finally exceeded 100 n/L in termination roller bottle cultures (data not shown). The piuified hlnimu31 from hlmmu31 pdHL2-transfected cells showed comparable immunoieactivity as t of its murine and chimeric counterparts (Fig. 6C). Example 7. Therapy of a patient with hepatocdiuar carcinoma with radiolabeled humanized antl-AFF monoclonal antibody. A 57-year-old man presenting with jaundice, malaise, loss of weight, and general weakness, is diagnosed witii an inoperable hepatocellular carcinoma that appears by computed tomography to extend about 6 cm in diameter in the rigt lobe of the liver, and to also appear as a single 3-cm lesion in the left lobe. His serum AFP level at &e time of presentation measures 150 ng/mL, with a 40% iiffiie£Ese in his serum transaminase and bilirubin levels, and a 50% increase in his seium LDH level. The right lobe lesion is confirmed by biopsy to be hepatocdltdar carcinonm expressing AFP. The patient is then given two cycles of humanized Imtnu31 monoclonal antibody conjugated by EMDTA vnih 9(KY, so that an infusion is administered for each Aerapy of a dose of 25 mCi (100 mg antibody protein). The first thery is given in an ouatient setting, and is repeated 6 weeks later. Prior to each tbery, a diagnostic dose of 111-In conjugated by DOTA to the antibody is also injected in order to demonstrate tumor targeting and to estimate the radiation dose delivered to the tumor and to other normal tissues, sacix as liver, kidney and bone marrow, so that the therjeutic dose with 90-Y, given a y/eek later, can be adjusted so as not to induce nonnal tissue/organ toxicity beyond what is considered tolerable (e.g,, 2000 cGy to kidneys). The patient is then monitored for response by repeated computer tomography scans every 4-8 weeks post therapy, as well as by serum AFP, bilirubin, transaniinase, and LDH levels. Eight we after the second therapeutic administration of the 90-Y-labeled antibody, his sum levels of bilirubin, transaminases, and LDH decreases to about 20% above normal, and his serum AFP titer is measured at 60 ng/mL, which also constitutes an improvement CT measurements of his liver disease shows an almost complete disappearance of the left lobe lesion and a 40% reduction of the larger mass in the right lobe. The patient then became a candidate fer surreal resection of his right lobe, since it is-considered that the remaining small lesion in the left lobe is not cancer, but scar tissue. This is fintber confirmed by a diagnostic study performed with 111-In-labeled hmnu31 antibody, which shows uptake in ibe right lobe mass but not in the left lobe, thus indicating that no AFP-expressii disease is in the left lobe. All of the publications and patent applications and patents cited in this specification are herein incorporated in their entirety by refoence. Although the foregoing refers to particular preferred embodiments, it will be understood that Hie present invention is not so limited. It will occur to iiiose of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the present invention, which is defined by the foUowing claims. WE CLAIM: 1. A humanized or chimeric monoclonal (MAb) antibody or fragment thereof that binds an alpha- fetoprotein (AFP) antigen, comprising the light chain complementarity-determining region (CDR) sequences CDRl KASQDINKYIG, CDR2 YTSALLP, CDR3 LQYDDLWT and the heavy chain CDR sequences CDRl SYVIH, CDR2 YIHPYNGGTKYNEKFKG and CDR3 SGGGDPFAY of the murine Immu31 antibody. 2. The antibody or fragment thereof as claimed in claim 1, comprising the complementarity-determining regions (CDRs) of the murine Immu31 antibody and the framework (FR) regions of the light and heavy chain variable regions of a human antibody and the light and heavy chain constant regions of a human antibody. 3. The antibody or fragment thereof as claimed in claim 2, wherein the FRs of the light and heavy chain variable regions of said antibody or fragment thereof comprise at least one amino acid substituted from the corresponding FRs of the murine anti-AFP antibody or fragment thereof 4. The antibody or fragment thereof as claimed in claim 3, wherein said amino acid from said murine MAb is at least one amino acid selected from the group consisting of amino acid residue 5, 27, 28, 30, 46, 48, 66, 67 and 94 of the murine heavy chain variable region of Fig. 4A. 5. The antibody or fragment thereof as claimed in claim 3, wherein said murine amino acids are at least one amino acid selected from the group consisting of amino acid residue 4, 39, 48, 49, 58, 69, 100 and 107 of the murine light chain variable region Fig. 4B. 6. The antibody or fragment thereof as claimed in claim 1, wherein said antibody or fragment thereof comprises the Immu31 VK nucleotide sequence of figure 2B, 7. The antibody or fragment thereof as claimed in claim 1, wherein said antibody or fragment thereof comprises the Immu31 VH nucleotide sequence of figure 2A, 8. The antibody or fragment thereof as claimed in claim 1, wherein said antibody or fragment thereof comprises a hlmmu31 VK nucleotide sequence of figure5B. 9. The antibody or fragment thereof as claimed in claim 1, wherein said antibody or fragment thereof comprises a hlmmuSl VH nucleotide sequence of figure 5A. 10. A CDR-grafted humanized heavy chain comprising the heavy chain complementarity determining regions (CDRs) of a murine Immu31 MAb and the framework region of the heavy chain variable region of a human antibody and the heavy chain constant region of a human antibody, wherein the heavy chain CDRs comprise CDRl comprising an amino acid sequence of SYVIH; CDR2 comprising an amino acid sequence of YIHPYNGGTKYNEKFKG and CDR3 comprising an amino acid sequence of SGGGDPFAY. 11. A CDR-grafted humanized light chain comprising the light chain complementarity determining regions (CDRs) of a murine Immu31 MAb and the framework region of the light chain variable region of a human antibody and the light chain constant region of a human antibody, wherein the light chain CDRs comprise CDRl comprising an amino acid sequence of KASQDINKYIG; CDR2 comprising an amino acid sequence of YTSALLP and CDR3 comprising an amino acid sequenceof LQYDDLWT. 12. The anti-AFP antibodies or fragment thereof as claimed in claim 1, wherein said fragment is selected from the group consisting of Fv, F(ab')2, Fab' and Fab. 13. An immunoconjugate comprising an antibody component that comprises an anti-AFP MAb or fragment thereof as claimed in claim 1 or an antibody fusion protein or fragment thereof that comprises the antibody as claimed in claim 1, wherein said antibody component is bound to at least one diagnostic/detection agent or at least one therapeutic agent. 14. The immunoconjugate as claimed in claim 13, wherein said diagnostic/detection agent comprises at least one photoactive diagnostic/detection agent. 15. The immunoconjugate as claimed in claim 13, wherein said therapeutic agent is selected from the group consisting of a radionuclide, boron, gadolinium or uranium atoms, an immunomodulator, a cytokine, a hormone, a hormone antagonist, an enzyme, an enzyme inhibitor, a photoactive therapeutic agent, a cytotoxic agent, a toxin, an angiogenesis inhibitor, a different antibody and a combination thereof. 16. The immunoconjugate as claimed in claim 15, wherein said cytotoxic agent is a drug or a toxin. 17. The immunoconjugate as claimed in claim 16, wherein said drug is selected from the group consisting of antimitotic, alkylating, antimetabolite, angiogenesis-inhibiting, apoptotic, alkaloid, COX-2-inhibiting and antibiotic agents and combinations thereof. 18. The immunoconjugate as claimed in claim 15, wherein said immunomodulator is selected from the group consisting of a cytokine, a stem cell growth factor, a lymphotoxin, a hematopoietic factor, a colony stimulating factor (CSF), an interferon (IFN), a stem cell growth factor, erythropoietin, thrombopoietin, an antibody and a combination thereof 19. The immunoconjugate as claimed in claim 13, wherein said diagnostic/detection or therapeutic agent is bound to said MAb or fragment thereof by means of a carbohydrate moiety. 20. A multivalent, multispecific antibody or fragment thereof comprising one or more humanized or chimeric antibodies or fragments thereof according to claim 1 and one or more hapten binding sites having affinity towards hapten molecules. 21. The antibody or fragment thereof as claimed in claim 20, further comprising a iiagnostic/detection or therapeutic agent. 22. An antibody fusion protein or fragment thereof comprising at least one first AFP MAb or fragment thereof as claimed in claim 1 and at least one second MAb or fragment thereof, other than the MAb or fragment thereof as claimed in claim 1, 23. The antibody fusion protein or fragment thereof as claimed in claim 22, wherein said second MAb binds to a tumor-associated antigen, 24. A DNA sequence comprising a nucleic acid encoding an anti-AFP MAb or fragment thereof selected from the group consisting of: (a) an anti-AFP MAb or fragment thereof of claim 1; (b) an antibody fusion protein or fragment thereof comprising at least two of said anti-AFP MAbs or fragments thereof; (c) an antibody fuasion protein or fragment thereof comprising at least one first anti-\FP MAb or fragment thereof of claim 1 and at least one second MAb or fragment hereof, other than the MAb or fragment thereof of claim 1; and (d) an antibody fusion protein or fragment thereof comprising at least one first MAb or fragment thereof comprising said MAb or fragment thereof of claim I and at least one second MAb or fragment thereof, wherein said second MAb binds to an antigen selected from the group consisting of CEA, EGP-1, EGP-2 MUC-1, MUC-2, MUC-3, MUC-4, KC4, rAG-72, EGFR, HER2/neu, BrE3, Le-Y, A3, Ep-CAM, Tn, Thomson-Friedenreich antigen, tumor necrosis antigen, tenascin, an oncogene, an oncogene product, IL-6, IGF-1, IGFR-1, a tumor angiogenesis antigen, vascular endothelium growth factor (VEGF), placental growth factor (PIGF), ED-B fibronectin, a vascular growth factor, ferritin, acidic isoferritin, Ga 733, or a combination thereof 25. The antibody or fragment thereof as claimed in claim 20, wherein said hapten is a carrier molecule comprising a diagnostic/detection agent, a therapeutic agent, or a combination thereof, that binds to a binding site of said antibody. 26. The antibody or fragment thereof as claimed in claim 20, wherein said antibody or fragment thereof is a naked antibody or fragment thereof 27. The antibody or fragment thereof as claimed in claim 26, wherein said chimeric, or humanized naked anti-AFP antibody constant and hinge regions comprise constant and hinge regions of a human IgGl. 28. The chimeric antibody or fragment as claimed in claim 1, wherein said antibody or fragment thereof comprises the Fv of Mab Iramu31, 29. A kit comprising : (A) a bispecific antibody or antibody fragment comprising at least one arm that specifically binds a targeted tissue and at least one other arm that specifically binds a targetable conjugate, wherein said one arm that specifically binds a targeted tissue is a humanized or chimeric antibody or fragment thereof according to claim 1; and (B) a targetable conjugate selected from the group consisting of (i) D0TA-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-NH2 ; (ii) DOTA-Phe-Lys (HSG)-Tyr-Lys(HSG)-NH2 ; (iii) Ac-Lys-(HSG)D-Tyr-Lys {HSG)-Lys{Tscg-Cys)-NH2; EMI133.1, EMU 34.1 30. The immunoconjugate as claimed in claim 13, wherein said therapeutic agent is a ribonuclease. 31. The immunoconjugate as claimed in claim 30, wherein said therapeutic agent is onconase. 32. A humanized or chimeric monoclonal (MAb) antibody or fragment thereof substantially as herein described and exemplified.

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