ANTIBODIES AGAINST HUMAN IL-12

Abstract: The present invention relates to p75 heterodimer specific anti-human IL-12 antibodies that are characterized by a higher potency and greater efficacy in neutralizing human IL-12 bioactivity than known heterodimer specific IL-12 monoclonal antibodies. The heterodimer specific antibodies recognize one or more epitopes of the human IL-12 p75 heterodimer, but do not bind to the p40 subunit alone. The heterodimer specific IL-12 antibodies neutralize rhesus monkey IL-12 bioactivity with a potency similar to their potency for neutralizing human IL-12 bioactivity making them useful IL-12 antagonists.

Description: ANTIBODIES AGAINST HUMAN IL-12 This invention relates generally to LL-12 antibodies, and more specifically to anti-human IL-12 polyclonal and monoclonal antibodies. Interleukin-12 (IL-12), formerly known as cytotoxic lymphocyte maturation factor or natural killer cell stimulatory factor, is a 75-kDa (p75) heterodimeric cytokine composed of disulfide bonded 40-kDa (ρ40) and 35-kDa (p35) subunits. The p40 and p35 subunits are polypeptides which contain 306 amino acid residues and 197 amino acid residues, respectively (Gubler U., et al., Proc. Natl. Acad. Sci. USA, Vol. 88, 4143-4147 (1991)). The p75 heterodimer is the biologically active form of IL-12 (Gubler, U., et al., 1991, Proc. Natl. Acad. Sci. USA, 88: 4143; Wolf, S.F., et al., 1991, J. Immunol., 146: 3074). The IL-12 p75 heterodimer both activates and boosts cell mediated immune responses against foreign antigens by stimulating production of Thl helper cells, stimulating activated T and natural killer (NK) cells, enhancing lytic activity of NK/LAK cells, and stimulating production of IFN-γ by resting and activated T and NK cells. The p40 subunit of IL-12 has been shown to be produced in excess of the p35 subunit and is found in both monomeric and dimeric forms (Podlaski, F.J., et al., 1992, Arch. Biochem. Biophys. 294: 230; D'Andrea, A., et al., 1992, J. Exp. Med., 176: 1387). IL-12 p40 homodimer is a potent IL-12 antagonist (Ling, P., et al , 1995, J. Immunol., 154: 116; Gillessen, S., et al , 1995, Eur. J. Immunol., 25: 200). In contrast to the p40 subunit, the p35 subunit of IL-12 has no known biological activity, and the p35 protein has only been found in association with the p40 subunit as part of the D -12 p75 heterodimer. Therefore, there are two important types of epitopes presented by human IL-12: (1) epitopes presented by the p40 subunit; and (2) epitopes presented by the three dimensional conformation of the IL-12 p75 heterodimer. Consequently, we designate antibodies that recognize epitopes present on the LL-12 p75 heterodimeric protein but do not recognize epitopes present on the IL-12 p40 subunit protein so called "heterodimer specific" antibodies. It has been found that known IL-12 antibodies are not optimally effective in substantially neutralizing IL-12 bioactivity. IL-12 antibodies which immunologically react with the p40 subunit do not optimally block the bioactivity of human IL-12. For example, use of antibodies which react with epitopes presented by the p40 subunit is particularly problematic because production of IL- 12 p75 heterodimer has been shown to result in excess inactive p40 subunits relative to bioactive p75 heterodimer (Podlaski, F.J., 1992, Arch. Biochem. Biophys. 294: 230; D'Andrea, A., et al., 1992, J. Exp. Med., 176: 1387). As a result, the p40 antibodies are not as effective as heterodimer specific antibodies in reducing detrimental effects of LL-12 because the p40 subunit alone is not bioactive, and p40 antibodies tend to bind to the inactive p40 subunits rather than those p40 subunits that are part of a bioactive p75 heterodimer. Even known antibodies which react only with the p75 heterodimer, do not effectively neutralize IL-12 bioactivity. For example, a previously identified IL-12 p75 heterodimer specific antibody, called 20C2 (Chizzonite et al., Cytokine, 6: A82a (1994) and D'Andrea et al., J. Exp. Med., Vol. 176, 1387-1398 (1992) ), cannot substantially block human IL-12 stimulated PHA-activated lymphoblast proliferation and IFN-γ production. Heterodimer specific antibodies which more effectively neutralize IL-12 bioactivity are needed to reduce detrimental effects of IL-12. Increased levels of IL-12 in serum or tissue are known to be involved in the development and progression of autoimmune disorders. Thus, IL-12 antibodies are useful antagonists for controlling diseases with pathologies that are mediated through immune mechanisms, particularly, diseases associated with aberrant Thl-type helper cell activity. Examples of such autoimmune disorders include multiple sclerosis, inflammatory bowel disease (D3D) including Crohn's disease and ulcerative colitis, rheumatoid arthritis and autoimmune diabetes mellitus. Other disease conditions which have been shown to benefit from the administration of IL-12 antibodies include transplantation/graft-versus-host disease and septic shock. In accordance with this invention, it has been found that IL-12 antibodies obtained from a mammal deficient in the gene encoding the p35 subunit and/or the gene encoding the p40 subunit substantially neutralize IL-12 bioactivity. In accordance with this invention, for the first time, antibodies which substantially neutralize the bioactivity of human LL-12 are produced using the methods described herein. Unlike other IL-12 p75 heterodimer specific antibodies, the heterodimer specific antibodies of the present invention neutralize at least 90% of human LL-12 bioactivity. In addition, IL-12 p75 heterodimer specific antibodies of the present invention cross react with rhesus monkey LL-12. The p75 heterodimer specific LL-12 antibodies described herein are effective therapeutic agents for use in blocking LL-12 bioactivity to treat conditions mediated by undesirable IL-12 stimulated immunological responses. The highly neutralizing heterodimer specific LL-12 antibodies described herein are particularly useful inhibitors of LL-12 stimulated PHA-activated human lymphoblast proliferation and EFN-γ production by PHA-activated human lymphoblasts. Fig. 1 is a graph showing capture of 125j_ι a b e led human LL-12 by antibodies contained in supernatants from hybridomas HLL-12F3-5F2 (herein referred to as "5F2"), HTL-12F3-16F2 (herein referred to as "16F2"), HLL-12F3- 16G2 (herein referred to as "16G2"), HTL-12F3-20E11 (herein referred to as "20E11"), and H3L-12F1-17E2 (herein referred to as "17E2) (open bars). The presence of unlabeled human LL-12 p40 subunit during the immunoprecipitation reaction (solid bars) did not block capture of 125j_ ι a b e ] ec [ human IL-12 by monoclonal antibodies 5F2, 16F2, 16G2 and 20E11, demonstrating that these antibodies do not have high affinity for the LL-12 p40 subunit alone. . Fig. 2 shows isoelectric focusing patterns of p75 heterodimer specific anti- human IL-12 monoclonal antibodies 20C2, 16G2, 16F2, 20E11, and 5F2. As shown in Fig. 2, monoclonal antibodies 20C2, 20E11 and 5F2 are unique immunoglobulins. Monoclonal antibodies 16G2 and 16F2 appear identical by isoelectric focusing, but both are different from 20C2, 20E11 and 5F2. Fig. 3 is a plot showing inhibition of natural human LL-12 stimulated PHA- activated human lymphoblast proliferation by p75 heterodimer specific IL-12 monoclonal antibodies 20C2 (+), 16G2 (Δ), 16F2 (O), 20E11 (+), and 5F2 (A). Inhibition of natural human LL-12 stimulated PHA-activated human lymphoblast proliferation was determined with respect to the level of 0.25 ng/ml human LL-12 stimulated PHA-activated human lymphoblast proliferation in the absence of LL- 12 antibodies, shown in Fig. 3 as a horizontal dotted line at 9940 cpm, and background levels of PHA-activated human lymphoblast proliferation, i.e., in the absence of both LL-12 and LL-12 antibodies, shown in Fig. 3 as a horizontal dotted line at 1480 cpm. As shown in Fig. 3, LL-12 monoclonal antibodies, 16G2 (Δ), 16F2 (O), 20E11 (+) and 5F2 (A) inhibit 0.25 ng/ml human LL-12 stimulated PHA-activated lymphoblast proliferation by at least 90%. In contrast, as shown in Fig. 3, previously known 20C2 (+) antibody does not substantially inhibit LL-12 stimulated PHA-activated human lymphoblast proliferation. Fig. 4 is a plot showing inhibition of rhesus monkey LL-12 stimulated PHA- activated human lymphoblast proliferation by p75 heterodimer specific LL-12 monoclonal antibodies 16G2 (Δ), 16F2 (O) , 20E11 (+) and 5F2 (A) of the present invention compared to the previously known 20C2 (+) antibody. The level of lymphoblast proliferation in the presence of 0.5 ng/ml rhesus monkey LL-12 and in the absence of LL-12 antibodies is represented by the horizontal dotted line at the upper end of the plot. The background level of lymphoblast proliferation, i.e., in the absence of both LL-12 and LL-12 antibodies is represented by a horizontal dotted line at the lower end of the plot. As shown in Fig. 4, the antibodies of the present invention are potent inhibitors of rhesus monkey LL-12 stimulated PHA- activated lymphoblast proliferation, in contrast to the 20C2 (+) antibody which has a minimal inhibitory effect on rhesus monkey LL-12 stimulated lymphoblast proliferation. Fig. 5 is a plot showing inhibition of IFN-γ production by p75 heterodimer specific monoclonal antibodies, 16F2 (O), 16G2 (■), 20E11 (A), 5F2 (•) and 20C2 (*). As shown in Fig. 5, antibodies 16F2 (O), 16G2 (■), 20E11 (A) and 5F2 (•) inhibit 0.25 ng/ml human LL-12 stimulated LFN-γ production by at least 90%. The dashed horizontal line at the lower end of the plot represents background EFN- γ production in the absence of LL-12. In contrast, as shown in Fig. 5, the 20C2 (#) monoclonal antibody is unable to inhibit 0.25 ng/ml LL-12 stimulated LFN-γ production by more than 65%. Fig. 6 is a nucleotide sequence encoding a portion of the heavy chain variable region of the p75 heterodimer specific 16G2 antibody, and the amino acid sequence deduced from this nucleotide sequence. Fig. 7 is a nucleotide sequence encoding a portion of the heavy chain variable region of the p75 heterodimer specific 20E11 antibody, and the amino acid sequence deduced from this nucleotide sequence. In accordance with the present invention, it has been found that when LL-12 antibodies are produced from mammals deficient in the gene encoding the p35 LL- 12 subunit and/or the gene encoding the p40 LL-12 subunit, LL-12 antibodies are obtained which selectively immunologically react with epitopes of the p75 heterodimer of LL-12, and are identified by their ability to selectively immunologically react with the p75 heterodimer of human LL-12, but not immunologically react with the p40 subunit alone. Unlike previously known LL-12 p75 antibodies, antibodies which substantially neutralize the bioactivity of human LL-12, i.e., neutralize at least about 90% bioactivity of human LL-12, are produced by the methods described herein. In addition, LL-12 p75 heterodimer specific antibodies of the present invention cross react with rhesus monkey LL-12. The LL-12 antibodies described herein neutralize at least about 90% bioactivity of human LL-12 by inhibiting at least about 90% LL-12 induced PHA- activated human lymphoblast proliferation at concentrations of at least about 0.5 μg/ml, and/or inhibiting at least about 90% of LL-12 stimulated LFN-γ production by PHA-activated human lymphoblasts at concentrations of at least about 0.5 μg/ml. Furthermore, the antibodies described herein have been shown to specifically inhibit LL-12-induced, but not LL-2-induced, proliferation of PHA- activated human lymphoblasts. PHA-activated lymphoblasts are prepared as follows. Peripheral blood mononuclear cells (PBMC) were isolated (Gately et al., J. Natl. Cancer Inst., 69:1245 (1982)) and stimulated with 0.1% PHA-P (Difco Labs., Detroit , MI). After 3 days, the cultures were split 1 : 1 with fresh medium and recombinant 50 U/ml human LL-2 as described in Gately, M.K., Chizzonite, R. and Presky, D.H., Measurement of human and mouse interleukin 12, Current Protocols in Immunology, vol. 1. J.E. Coligan, A.M. Kruisbeek, D.H. Margulies, E.M. Shevach, and W. Strober, eds., John Wiley & Sons, Inc., New York, 1995, pp. 6.16.1-6.16.15. The PHA-activated lymphoblasts were used after an additional one day incubation period. In accordance with the present invention, the IL-12 antibodies are identified for their ability to selectively bind the epitope presented by the p75 heterodimer, but not immunologically react with any epitope presented by the p40 subunit. This selectivity is defined by the fact that the LL-12 antibodies of this invention will react, at a certain minimal concentration, with an epitope solely presented by a given amount of the p75 heterodimer but will not react at that concentration with an epitope presented by the p40 subunit of that same given amount of this p75 heterodimer. In this way the antibodies of this invention have a higher affinity for an epitope solely presented by the p75 heterodimer than any epitope presented by the p40 subunit. Any conventional assay for identifying selective binding of the antibodies to the p75 heterodimer can be used. Generally, in such an assay, antibodies are incubated with human IL-12 p75 heterodimer to determine if the antibodies bind the p75 heterodimer. The antibodies are also incubated with human LL-12 p75 heterodimer in the presence and absence of the p40 subunit to determine if the presence of the p40 subunit blocks antibody binding or capture of the p75 heterodimer. For example, competitive immunoprecipitation assays (see Example 7 herein) can be used to demonstrate that the antibodies described herein selectively immunologically react with the p75 heterodimer of human LL-12, but are not immunologically reactive with the p40 subunit alone. In accordance with the present invention, the LL-12 antibodies described herein are produced through the use of knock-out mammals. The knock-out mammals are deficient in the gene encoding the p35 subunit and/or the gene encoding the LL-12 p40 subunit and thus, do not express the LL-12 p75 heterodimer. When immunized with the IL-12 p75 heterodimer, the IL-12 p35 subunit deficient and/or the LL-12 p40 subunit deficient knock-out mammal recognizes the LL-12 p75 heterodimer as foreign and produces antibodies thereto. Preferably, the knock-out mammal is a mouse. In accordance with the present invention knock-out mammals are produced by methods that have been described in the art. Knock-out mammals can be produced by conventional means such as by mutation of the gene encoding the p35 LL-12 subunit and/or the p40 LL-12 subunit. For example, mice carrying a mutation in the LL-12 p35 subunit gene can be produced as described by Mattner, F., et al., Eur. J. Immunol., 26:1553-1559 (1996). Mice carrying a mutation in the LL-12 p40 subunit gene can be produced as described by Magram, J., et al., Immunity, 4: 471-481 (1996). In accordance with the present invention, polyclonal and monoclonal antibodies that selectively immunologically react with the p75 heterodimer of human LL-12 are produced from activated cells of the aforementioned knock-out mammal by any conventional means known in the art. Generally, the antibodies are produced by (a) immunizing a "knock-out" mammal deficient in a gene encoding the p35 subunit and/or the p40 subunit with human p75 heterodimer to produce antibodies; (b) obtaining antibodies from the immunized mammal; and (c) screening the antibodies for their ability to selectively bind the epitope presented by the p75 heterodimer to obtain the selectively binding antibodies. The LL-12 monoclonal antibodies of the present invention which selectively immunologically react with the human LL-12 p75 heterodimer are generally produced by a method including the following steps: (1) immunizing a knock-out mammal, such as, for example, a mouse deficient in the gene encoding the IL-12 p35 subunit and/or LL-12 p40 subunit, with human LL-12 p75 heterodimer; (2) selecting cells from the immunized knock-out mammal that have been activated to express antibodies against LL-12, such as, splenocytes or lymph node cells; (3) fusing the harvested cells to myeloma cells to form hybridoma cells; (4) selecting hybridoma cells which secrete antibodies that recognize human LL-12, for example, by testing hybridoma conditioned medium for the presence of anti-human LL-12 antibodies, for example, through the use of ELISA or immunoprecipitation assays employing labeled or unlabeled human LL-12; and (5) determining if the antibodies are p75 heterodimer specific by demonstrating that the antibodies immunologically react with an epitope of the p75 LL-12 heterodimer, but are not immunologically reactive with any epitope of the p40 subunit, by incubating the antibodies with human LL-12 p75 heterodimer to determine if the antibodies bind the p75 heterodimer, and then incubating the antibodies with human LL-12 p75 heterodimer in the presence and absence of the p40 subunit to determine if the presence of the p40 subunit blocks antibody binding or capture of the p75 heterodimer. For example, competitive immunoprecipitation assays (see Example 7 herein) can be used to demonstrate that the antibodies described herein selectively immunologically react with the p75 heterodimer of human LL-12, but are not immunologically reactive with the p40 subunit alone. The method for producing the p75 heterodimer specific LL-12 monoclonal antibodies of the present invention can further comprise the step of determining the ability of the heterodimer specific LL-12 antibodies to inhibit both human and rhesus monkey LL-12 bioactivity in any in vitro or in vivo assay system for LL-12 bioactivity, such as assays for determining LL-12-stimulated proliferation of activated lymphocytes, LL-12-stimulated production of EFN-γ, or LL-12-stimulated enhancement of cytolytic activity. The anti-human LL-12 antibodies of the present invention can be isolated to substantially pure form by standard methods known in the art, such as, for example, ammonium sulfate precipitation, affinity chromatography, or ion exchange chromatography. Variations of the method for obtaining the antibodies of the present invention are also encompassed within the present invention. Methods known in the art such as, for example, Western blotting, competitive immunoprecipitation assays, or cross-blocking binding assays can be used to determine if the antibodies are p75 heterodimer specific. In addition to mice, mammals such as rats and rabbits deficient in the LL-12 p35 subunit gene and/or LL-12 p40 subunit gene, can be immunized with the LL-12 p75 heterodimer to produce the antibodies described herein. The deficiency or mutation in the LL-12 p35 subunit gene and/or LL-12 p40 subunit gene can be any deficiency or mutation that results in lack of expression of LL-12 p75 heterodimer. Furthermore, any conventional method for obtaining mammalian cells carrying a mutation in the LL-12 p35 subunit gene and/or LL-12 p40 subunit gene which results in LL-12 p75 deficient phenotype can be used. In accordance with the present invention, activated mammalian cells expressing antibodies to the human LL-12 p75 heterodimer can be obtained by immunizing a mouse or other mammal with natural human LL-12 or recombinant LL-12. Natural human LL-12 and recombinant human LL-12 can be prepared by any conventional technique known in the art, such as the techniques provided in the examples herein. Suitable myeloma cell lines, i.e., fusion partners, for use in producing the hybridomas that secrete the LL-12 antibodies of the present invention include myeloma cell lines well known in the art, such as, for example, SP 2/0 and NS/O cell lines. SP2/0 mouse myeloma cells are preferred. Preferably, the myeloma fusion partner and the mammalian cell activated against the LL-12 p75 heterodimer are derived from the same species. Hybridoma cells producing the antibodies of the present invention can be selected and isolated by any conventional methods known in the art. Preferably, myeloma cells and lymphocytes activated against the LL-12 p75 heterodimer are cultured together in media containing a selection agent capable of killing the myeloma cells but not the lymphocytes. Hybridomas are formed from myeloma cells that fuse with the lymphocytes activated against the LL-12 p75 heterodimer. Such hybridoma cells are capable of growing in the media containing the selection agent because DNA of the lymphocytes supplies to the myeloma cell line the necessary gene encoding an enzyme that prevents the toxic effects of the selection agent by allowing an alternate metabolic pathway to replace the metabolic pathway blocked by the selection agent. Any unfused lymphocytes die because they are not transformed and have short, finite lifetimes in vitro. In accordance with the present invention a suitable selection agent for use in selecting out hybridoma cells is aminopterin. A preferred medium for cultivating the hybridoma cells is Iscove's Modified Dulbecco's Medium (LMDM) supplemented with 10% FBS (Hyclone), 100 Units/ml penicillin G (BioWhittaker), 100 μg/ml streptomycin (BioWhittaker), 250 ng/ml Fungizone (BioWhittaker), 2 mM glutamine (BioWhittaker), 100 μg/ml gentamicin sulfate (BioWhittaker), 50 μM 2-mercaptoethanol (BioRad), 100 μM hypoxanthine (Sigma), 400 nM aminopterin (Sigma), 16 μM thymidine (Sigma), and 2.5% P388D1 supernatant (produced as described by Nordan, R.P., et al., J. Immunol., 139:813 (1987)). The potency of the LL-12 antibodies of the present invention is determined with respect to the concentration of LL-12 antibodies at which 50% oLmaximal inhibition of LL-12 bioactivity occurs as measured by LL-12-stimulated human lymphoblast proliferation or IFN-γ production assays. The anti-human LL-12 antibodies of the present invention exhibit higher potency than previously characterized heterodimer specific LL-12 antibodies. In addition, the anti-human antibodies of the present invention exhibit greater efficacy, as measured by the extent of maximal inhibition of LL-12-stimulated lymphocyte proliferation or IFN-γ production, than previously characterized heterodimer specific LL-12 antibodies. The potency and efficacy of the antibodies described herein can be determined by any conventional assay known in the art, such as, for example, LL-12 induced lymphoblast proliferation assays or LFN- γ synthesis assays. In accordance with the present invention, any conventional method known in the art can be used to determine inhibition of human LL-12 stimulated lymphoblast proliferation by the LL-12 antibodies. In general, human lymphocytes can be activated by a number of methods, including treatment with mitogenic lectins, e.g. phytohemagglutinin A (PHA), or other activating agents, alone or in combination, such as cytokines, phobol esters and ionophores, antibodies directed against cell surface molecules, or any other method which will lead to activation of the lymphocytes. The activated lymphocytes are then incubated with and without LL-12 in the absence or presence of the antibodies, and the rate of lymphocyte proliferation is measured by determining the rate of DNA synthesis by measuring the incorporation of 3 H-thymidine into DNA, by counting the number of cells present after various periods of treatment, or any other method that can be used to monitor the rate of cellular proliferation. Inhibition of proliferation is determined by comparing lymphocyte proliferation at a defined concentration of LL-12 in the absence and presence of various concentrations of anti-LL-12 antibodies. In a standard lymphocyte proliferation assay, inhibition of human LL-12 stimulated PHA-activated human lymphoblast proliferation is determined with respect to levels of human LL-12 stimulated PHA-activated human lymphoblast proliferation without any added antibodies and background levels of PHA-activated human lymphoblast proliferation, i.e., proliferation in the absence of both LL-12 and antibodies. In general, LL-12-stimulated levels of proliferation yield about 10,000- 80,000 cpm in our standard human lymphocyte proliferation assay, with background levels of proliferation yielding about 5,000-20,000 cpm. Due to the inherent variability between batches of stimulated PHA-activated human lymphoblasts, only assays in which the ratio of stimulated proliferation to background proliferation (i.e. the stimulation index) was equal to or greater than 3 are considered valid for the measurment of LL-12-stimulated proliferation. In accordance with the present invention, any conventional method for determining inhibition of IFN-γ production by the LL-12 antibodies can be used. For example, activated human lymphocytes, prepared as described herein, or activated human peripheral blood mononuclear cells (PBMC), prepared by treating whole blood or isolated PBMC with mitogenic agents including lectins, cytokines, phobol esters, ionophores, or antibodies directed against cell surface molecules, alone or in combination, or by any other method which will lead to the production of activated human PBMC, are incubated with or without LL-12 and various other agents, e.g. JL-2 and/or LL-lβ, in the absence and presence of the antibodies. IFN-γ production is then determined, e.g. by sampling the culture medium and determining the concentration of IFN-γ by ELISA or any other method that can quantitatively measure IFN-γ. Inhibition of LFN-γ production is determined by comparing IFN-γ production at a defined concentration of LL-12 in the absence and presence of various concentrations of anti-LL-12 antibodies. In a standard IFN-γ synthesis assay inhibition of IFN-γ is determined with respect to LL-12-stimulated IFN-γ production and background levels of IFN-γ production, i.e., IFN-γ synthesis in the presence or absence of LL-12. In general, LL-12-stimulated levels of IFN-γ production are about 7-220 ng/ml, with background levels of production yielding about 1-3 ng/ml. The antibodies herein neutralize rhesus monkey IL-12 bioactivity with a potency similar to their potency for inhibiting human LL-12 bioactivity, making them useful LL-12 antagonists for in vivo studies in the rhesus monkey. The increased potency and efficacy of these anti-human LL-12 antibodies and their cross reactivity with rhesus monkey LL-12 make them excellent candidates for designing effective LL-12 antagonists for use in humans. In particular, the present invention provides four antibodies, 5F2, 16F2, 16G2 and 20E11 to the p75 heterodimer of human LL-12. The corresponding hybridoma cell lines producing these antibodies have been deposited on December 11, 1997 under the conditions of the Budapest Treaty at the American Type Culture Collection under ATCC accession numbers HB-12446, HB-12447, HB-12449, and HB-12448, respectively. However, the present invention is not limited to these four antibodies. Any antibodies having the characteristics described herein are encompassed within the present invention. Fig. 6 provides the nucleotide sequence encoding a portion of the heavy chain variable region of the p75 heterodimer specific 16G2 antibody and the amino acid sequence deduced from this nucleotide sequence. The nucleotide sequence encoding a portion of the heavy chain variable region of the p75 heterodimer specific 20E11 antibody and the amino acid sequence deduced from this nucleotide sequence is provided in Fig. 7. It will be understood by those skilled in the art that conservative amino acid changes can be made in the constant regions of the heterodimer specific LL-12 antibodies herein without significantly affecting the antigen binding specificity/affinity. Heterodimer specific LL-12 antibodies containing amino acid changes in the variable framework regions or more specifically in the complementary determining regions can be expected to have a greater effect on antigen binding specificity/affinity. The LL-12 antibodies of the present invention can be complete antibodies including two full length heavy chains and two full length light chains. Alternatively, the LL-12 antibodies can be constructs such as single chain antibodies or "mini" antibodies that retain binding activity to one or more epitopes of the LL- 12 p75 heterodimer. Such constructs can be prepared by methods known in the art such as, for example, the PCR mediated cloning and assembly of single chain antibodies for expression in E. coli (as described in Antibody Engineering, The practical approach series, J. McCafferty, H.R. Hoogenboom, and D. J. Chiswell, editors, Oxford University Press, 1996). In this type of construct, the variable portions of the heavy and light chains of an antibody molecule are PCR amplified from cDNA. The resulting amplicons are then assembled, e.g. in a second PCR step, through a linker DNA that encodes a flexible protein linker composed of the amino acids GLY and SER. This linker allows the variable heavy and light chain portions to fold in such a way that the antigen binding pocket is regenerated and antigen is bound with affinities often comparable to the parent full-length dimeric immunoglobulin molecule. The anti-human LL-12 antibodies described herein may be humanized to form antibodies that possess the same or substantially similar affinity for the LL-12 p75 heterodimer as mammalian anti-human LL-12 antibodies, but are substantially non-immunogenic in humans. For example, a humanized LL-12 antibody in accordance with the present invention can include heavy and light chain framework regions of human antibodies. Preferably, the amino acid sequences of the humanized antibody framework regions are from about 60% to 95% identical to the donor framework regions. The humanized antibodies may be produced by recombinant techniques well known in the art. Methods for producing humanized immunoglobulins are described, e.g. in U.S. Patent No. 5,530,101. The LL-12 antibodies of the present invention are useful antagonists for controlling diseases with pathologies that are mediated through immune mechanisms, particularly, diseases associated with increased LL-12 bioactivity that results in aberrant Thl-type helper cell activity. In accordance with the present invention, the LL-12 antibodies are used for treating autoimmune disorders in humans or other mammals, such as, for example, multiple sclerosis, rheumatoid arthritis, autoimmune diabetes mellitus, and inflammatory bowel disease (LBD) including Crohn's disease and ulcerative colitis. The antibodies described herein can also be used to treat other disease conditions which have been shown to benefit from the administration of LL-12 antibodies including, for example, transplantation/graft-versus-host disease and septic shock. The dose ranges for the administration of the LL-12 antibodies herein may be determined by those of ordinary skill in the art without undue experimentation. In general, appropriate dosages are those which are large enough to produce the desired effect, i.e., neutralizing at least 90% LL-12 bioactivity. However, the dosage should not be so large as to cause adverse side effects, such as unwanted cross- reactions, anaphylactic reactions, and the like. Generally, the dosage will vary with the age, condition, sex and extent of disease in the patient, counter indications, if any, immune tolerance and other such variables, to be adjusted by the individual physician. The LL-12 antibodies may be administered parenterally by injection or by gradual perfusion over time. They can be administered intravenously, intramuscularly, or subcutaneously. Preparations for parenteral administration include sterile or aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic/aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringers' dextrose, dextrose and sodium chloride, lactated Ringer's, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers, such as those based on Ringer's dextrose, and the like. Preservatives and other additives may also be present, such as, for example, antimicrobials, anti-oxidants, chelating agents, inert gases and the like. See generally, Remington 's Pharmaceutical Science, 16th Ed., Mack Eds., 1980. Preferred dosages of the LL-12 antibodies of the present invention are from about 0.1 mg/kg to about 10 mg/kg, two to three times per week. However, the dosage and dosage schedule for administration of the LL-12 antibodies herein may vary depending on the individual to be treated, the antibody administered, and the variables discussed above. In accordance with the present invention, the LL-12 antibodies may be administered alone or in combination with other therapeutically active agents. EXAMPLES EXAMPLE 1 Preparation of Natural Human IL-12 Blood was drawn from normal volunteer donors into syringes containing preservative-free heparin (Sigma, St. Louis, MO, USA) to give a final concentration of ~ 5 units heparin/ml blood. One volume of heparinized blood was diluted into 9 volumes of medium consisting of a 1:1 mixture of RPMI 1640 and Dulbecco's modified Eagle's medium, supplemented with 0.1 mM nonessential amino acids, 60 μg/ml arginine HC1, 10 mM HEPES buffer, 2 mM L-glutamine, 100 U/ml penicillin, 100 μg/ml streptomycin (all available from GLBCO BRL, Grand Island, NY, USA), 50 μM 2-mercaptoethanol (Fisher Scientific, Fair Lawn, NJ, USA), and 1 mg/ml dextrose (Fisher). To this mixture was added human interferon-γ, 20 U/ml, (PeproTech, Inc., Rocky Hill, NJ, USA) and Pansorbin cells (formalinized Staphylococcus aureus, Cowan strain; Calbiochem, San Diego, CA, USA) at a final dilution of 1/4000. (Prior to use in the cultures, Pansorbin cells were washed 2 times with Dulbecco's phosphate-buffered saline (GLBCO BRL) and reconstituted to the same volume as supplied by the manufacturer.) The resulting cell suspension was aliquoted into 162 cm^ tissue culture flasks (Costar, Cambridge, MA, USA), 80 ml/flask, and the flasks were incubated horizontally at 37°C in a humidified atmosphere of 5% CO2/95% air for 24 hours. The culture supernatant fluids were then harvested by centrifugation and sterilized by filtration through a 0.22 μm filter (Costar). LL-12 heterodimer plus LL-12 p40 were purified from the culture supernatants by immunoaffinity chromatography using a 2-4A1 protein G sepharose (PGS) column, as described below for the purification of rhesus LL-12, except that the elution buffer contained 0.01% gelatin (Sigma) to minimize protein loss due to nonspecific adsorption to surfaces. The eluate was dialyzed for 4 to 6 hours against 100-200 volumes of Dulbecco's phosphate- buffered saline, and then overnight against the same volume of RPMI 1640 containing 100 μg/ml gentamicin. The dialyzed eluates were sterilized by passage through a 0.22 μm filter, and then assayed by ELISA for content of LL-12 heterodimer and LL-12 p40 (Gately, M.K., Chizzonite, R. and Presky, D.H., Measurement of human and mouse interleukin 12, Current Protocols in Immunology, vol. 1. J.E. Coligan, A.M. Kruisbeek, D.H. Margulies, E.M. Shevach, and W. Strober, eds., John Wiley & Sons, Inc., New York, 1995, pp. 6.16.1- 6.16.15) and for LL-12 bioactivity (ibid.). Typically, the weight ratio of LL-12 p40:LL-12 heterodimer, as measured by ELISA, was approximately 5: 1. EXAMPLE 2 Production of Recombinant Human IL-12 Recombinant Human LL-12 was prepared, characterized, and generated as set forth in U.S. Patent No. 5,536,657. EXAMPLE 3 Generation of Rhesus Monkey IL-12 The p35 and p40 subunit cDNA sequences for rhesus monkey LL-12 (F.Villinger et al., J. Immunol., 155:3946-3954 (1995)) were engineered for expression in CHO-dhfr minus cells on two separate plas ids using standard procedures (Current protocols in molecular biology, F. Ausubel, ed., J. Wiley and Sons, Inc., New York (1993)). Clones were obtained from an unamplified cell population and their LL-12 production was monitored by an LL-12 specific ELISA. An optimally producing clone was selected and adapted to growth in CHO serum- free medium (Sigma). The cells were subsequently grown in spinner cultures for protein production purposes. Rhesus monkey LL-12 was purified from the supernatants by antibody affinity chromatography. The affinity column was produced by crosslinking 10 mg of anti-human LL-12 p40 mAb 2-4A1 (Chizzonite et al., J. Immunol., 147:1548-1556 (1991)) to Protein G Sepharose (Pharmacia Biotech) using 10 mM dimethyl pimelimidate (Pierce, Rockford, LL, USA) at a density of 1 mg mAb/ml of gel (Stern and Podlaski, Tech. In Protein Chem. TV, Acad. Press, New York, 353-360 (1993)). The serum-free CHO supernatant containing rhesus LL-12 was filtered through a 0.2 μm filter and loaded directly onto the 10 ml 2-4A1 PGS column previously equilibrated in PBS pH 7.2. The flow rate was 1 ml/min. The column was washed with 10 volumes of PBS and eluted with 0.1M Glycine-HCL, 0.15M NaCl pH 3.0. The eluate was immediately neutralized with 3M Tris-HCl, pH 9. The affinity column was able to bind ~2 mgs of rhesus LL-12/run, including excess p40 monomer, as determined by Bradford and SDS-PAGE. Other contaminants were at trace levels. To concentrate and further purify the rhesus LL-12, the LL-12-containing eluate was dialzyed against 20 mM Na Phosphate, pH 7, and loaded onto a S-Sepharose column conditioned with the same buffer solution. The flow rate was 1 ml min. All protein was bound. The column was washed with 10 volumes of phosphate buffer and then eluted with phosphate buffer containing 0.3M NaCl. The eluted pool was assayed for endotoxin using the LAL kit from Biowittaker and found to be < 10 EU/mg of protein. Western Blot analysis using the mAb 2-4A1 as detection reagent showed the rhesus LL-12 heterodimer at -80 kDa as well as an apparent excess of p40 monomer at 40 kDa. Coomassie stained SDS-PAGE shows an additional prominent protein of equal intensity to the p80 heterodimer at -70 kDa. Both the 80 and 70 kDa proteins are reduced to their monomeric forms after treatment with 2-mercaptoethanol but the latter protein band does not react with mAb 2-4A1. EXAMPLE 4 Preparation, Characterization, and Purification of Hybridoma Antibodies Mice carrying a mutation in the LL-12 p35 subunit gene on the Balb/c background were produced as described in Mattner, F., et al., Eur. J. Immunol., 26:1553-1559 (1996). The LL-12 p35-deficient mice were immunized intraperitonealy with 5 μg of purified recombinant human LL-12 in complete Freund's adjuvant. The mice received 3 subsequent intraperitoneal booster injections of 5 μg human LL-12 in incomplete Freund's adjuvant over a 2.5 month period. Final injections of 75 μg human LL-12 in PBS (50 μg i.p. and 25 μg i.v.) were given three and two days before splenectomy, followed by an i.p. injection of 50 μg of human LL-12 in PBS one day before splenectomy. Splenocytes were harvested from these mice and fused to mouse myeloma SP2/0 cells at a ratio of 1 : 1 using 50% w/v polyethylene glycol 1500 (Boehringer Mannheim) according to the method of Oi and Herzenberg, in Selected Methods in Cellular Immunology, ed. B. Mishell and S. Shiigi, W. H. Freeman and Co., New York, 1980, pp.351 - 372. The fused cells were plated at a density of 60,000 total cells/well in 96-well cluster plates in LMDM supplemented with 10% FBS (Hyclone), 100 Units/ml penicillin G (BioWhittaker), 100 μg/ml streptomycin (BioWhittaker), 250 ng/ml Fungizone (BioWhittaker), 2 mM glutamine (BioWhittaker), 100 μg/ml gentamicin sulfate (BioWhittaker), 50 μM 2-mercaptoethanol (BioRad), 100 μM hypoxanthine (Sigma), 400 nM aminopterin (Sigma), 16 μM thymidine (Sigma), and 2.5% P388D1 supernatant (produced as described by Nordan, R.P., et al., J. Immunol., 139:813 (1987)). Hybridoma supernatants were assayed for specific anti-human LL-12 antibodies by immunoprecipitation of 125τ_ι a b e ι ec ι human LL-12 as described below. Hybridoma cell lines secreting anti-human LL-12 antibodies were cloned by limiting dilution. Antibodies were purified from ascites by sequential treatment with caprylic acid and ammonium sulfate as previously described (Reik, L. et al., J. Immunol. Methods, 100: 123-130 (1987)). EXAMPLE 5 Preparation of 125ι_ι aDe led Human IL-12 Recombinant human LL-12 was radiolabeled to a specific activity of about 2200 Ci/mmol using a modification of the lodogen (Pierce Chemical Co.) procedure previously described in Chizzonite et al., J. Immunol. ,147: 1548-1556 (1991) and Chizzonite et al., J. Immunol., 148: 3117-3124 (1992) which are incorporated herein by reference. lodogen was dissolved in chloroform and 0.05 mg dried in a 12 x 15 mm borosilicate glass tube. For radiolabeling, 1.0 mCi Na[ 125 I] (Amersham, Chicago, DI., USA) was added to an Iodogen-coated tube containing 0.05 ml of Tris-iodination buffer (25 mM Tris-HCL pH 7.5, 0.4 M NaCl and ImM EDTA) and incubated for 6 min at room temperature. The activated 125 I solution was transferred to a tube containing 0.1 ml LL-12 (31.5 μg) in Tris-iodination buffer and the reaction was incubated for 6 minutes at room temperature. At the end of the incubation, 0.05 ml of lodogen stop buffer (10 mg/ml tyrosine, 10% glycerol in Dulbecco's PBS, pH 7.40) was added and reacted for 5 minutes. The mixture was then diluted with 1% (w/v) BSA in 1.0 ml Tris-iodination buffer, and applied to a Bio-Gel P10DG desalting column (BioRad Laboratories (BRL)) for chromatography. The column was eluted with 1% (w/v) BSA in Tris-iodination buffer, and fractions (1 ml) containing the peak amounts of labeled protein were combined and diluted to lxlO 8 cpm/ml with 1% (w/v) BSA in Tris-iodination buffer. The TCA preciptable radioactivity (10% TCA final concentration) was typically in excess of 95% of the total radioactivity. The radiospecific activity of the recombinant human LL-12 was typically about 2200 Ci/mmol. EXAMPLE 6 Immunoprecipitation Assay of ^^^I-labeled Human IL-12 Nunc Maxisorp 96-well break-apart plates were coated with rabbit affinity purified antibody to mouse IgG (Cappel, Durham, NC, USA) by incubating 18 hrs at 4° C with 100 μl/well of 5μg/ml rabbit anti-mouse IgG in carbonate coating buffer (15 mM Na CO 3 / 35 mM NaHCO 3 ), pH 9.6. The coated wells were washed with PBS /0.05% Tween-20/0.01% Thimerosol and then blocked by incubation with 200 μl of 1% (w/v) BSA PBS/0.01% Thimerosol for 4 hrs at 37° C. Hybridoma supernatants (75μl) were added to the anti-mouse IgG-coated wells and incubated for 3 hrs at 22° C. The wells were washed 3 times with 300 μl of PBS/0.05% Tween-20/0.01% Thimerosol, and then 100,000 cpm of 125 I-labeled human LL-12 were added to each well in 100 μl of antibody diluting buffer (PBS/1% BSA (w/v)/0.5 M NaCl/0.05% Tween-20/0.01% Thimerosol). After 18 hrs at 4° C, the wells were washed 3 times with 200 μl of PBS/0.05% Tween- 20/0.01% Thimerosol. The wells were then separated and the amount of radioactivity bound to the wells was determined using a gamma counter. In some experiments, following the incubation of the hybridoma supernatants in the rabbit anti-mouse IgG-coated wells, 100 μl of conditioned supernatant from human LL-12 p40-transfected COS cells prepared as previously described (Gubler et al., Proc. Natl. Acad. Sci. 88: 4143-4147 (1991)) were incubated in the wells for 1 hr at 37° C prior to addition of 125τ_ι aDe ι e d human LL-12 to determine if the captured mouse anti-human LL-12 antibodies bound to the p40 subunit of human LL-12. EXAMPLE 7 Identification of Monoclonal Anti-Human IL-12 Antibodies A 96-well plate-based immunoprecipitation assay was used to identify hybridomas secreting anti -human LL-12 antibodies. Hybridoma supernatants were incubated in the absence and presence of lOOμl COS cell supernatant containing human LL-12 p40 subunit as described above. ^-^I-\ be.\ ά human LL-12 (100,000 cpm/well) was added, and the amount of 1— ^I-labeled human LL-12 captured onto the wells was determined. Fig. 1 shows that antibodies contained in supernatants from hybridomas 5F2, 16F2, 16G2, 20E11 and 17E2 captured 125 I-labeled human LL-12. In addition, the presence of unlabeled human LL-12 p40 subunit during the immunoprecipitation reaction did not block capture of 12^1-labeled human LL-12 by the antibodies 5F2, 16F2, 16G2 and 20E11, demonstrating that these antibodies do not have high affinity for the LL-12 p40 subunit alone. In contrast, the presence of unlabeled human LL-12 p40 subunit during the immunoprecipitation reaction completely blocked capture of 125τ_ι a be] e d human LL-12 by 17E2, demonstrating that 17E2 recognized the p40 subunit of human LL-12. EXAMPLE 8 Analytical Isoelectric Focusing of Anti-Human IL-12 Monoclonal Antibodies Analytical isoelectric focusing was performed using a pH 3.5-9.5 Ampholine PAGplate from Pharmacia Biotech (code no. 80-1124-80, Uppsala, Sweden). Isoelectric focusing was done according to the manufacturer's instructions using electrode solutions of 1 M phosphoric acid and IN sodium hydroxide. The gel was loaded with 5 samples, each of which contained a single immunoglobulin, i.e., 20E11, 5F2, 20C2, 16G2 and 16F2. Standards were from the Isoelectric Focusing pH 3-10 Calibration Kit from Pharmacia Biotech (code no. 17- 0471-01). Running conditions were 1000 volts, 10 watts, 2.5 hours, 4°C. The gel was silver stained using the Pharmacia Biotech PlusOne Silver Staining Kit for protein (code no. 17-1150-01) according to the manufacturer's directions. Fig. 2 shows the isoelectric focusing patterns of an ti -human LL-12 monoclonal antibodies 20C2, 16G2, 16F2, 20E11, and 5F2. EXAMPLE 9 Isoelectric Focusing Patterns of the Anti-Human IL-12 Monoclonal Antibodies As shown in Fig. 2, monoclonal antibodies 20C2 (Chizzonite et al., Cytokine, 6: A82a (1994)), 20E11, and 5F2 are unique immunoglobulins. Monoclonal antibodies 16G2 and 16F2 appear identical by isoelectric focusing, but both are different from 20C2, 20E11 and 5F2. The pi of these antibodies is in the range of pH 5-6. EXAMPLE 10 Generation of PHA- Activated Lymphoblasts Day 4 PHA-activated human peripheral blood mononuclear cells (PBMC) were used in determining both natural human IL-12-induced and rhesus monkey LL- 12-induced proliferation. PBMC were isolated (Gately et al., J. Natl. Cancer Inst., 69:1245 (1982)) and stimulated with 0.1% PHA-P (Difco Labs., Detroit , MI, USA). After 3 days, the cultures were split 1:1 with fresh medium and recombinant 50 U/ml human EL-2 as described (Gately, M.K., Chizzonite, R. and Presky, D.H., Measurement of human and mouse interleukin 12, Current Protocols in Immunology, vol. 1. , J.E. Coligan, A.M. Kruisbeek, D.H. Margulies, E.M. Shevach, and W. Strober, eds., John Wiley & Sons, Inc., New York, 1995, pp. 6.16.1-6.16.15). Supplemented medium used for cell culture was as described previously for the production of natural human LL-12 with the addition of 5% human AB serum (Irvine Scientific, Santa Ana, CA, USA). EXAMPLE 11 Lymphocyte Proliferation Assay The effects of the various anti-human LL-12 monoclonal antibodies on LL-12- and LL-2-stimulated PHA-activated human lymphoblast proliferation was determined by a method based on M. K. Gately et al. (Gately, M.K., Chizzonite, R. and Presky, D.H., Measurement of human and mouse interleukin 12, Current Protocols in Immunology, vol. 1., J.E. Coligan, A.M. Kruisbeek, D.H. Margulies, E.M. Shevach, and W. Strober, eds., John Wiley & Sons, Inc., New York, 1995, pp. 6.16.1-6.16.15). Day 4 PHA-activated lymphoblasts, prepared as described above, were harvested, washed and resuspended in supplemented medium at 4 x 10^ cells/ml and incubated in 96-well plates (2 x 10^ cells/well) with purified monoclonal anti-human LL-12 antibody and the relevant cytokine, i.e. human or monkey LL-12. Twenty five μl aliquots of both natural human LL-12 at 1 ng/ml or monkey LL-12 at 2 ng/ml were mixed with 25 μl aliquots of various dilutions of anti-human LL-12 monoclonal antibodies (mAbs). The final antibody concentration in the wells varied from 0.0005 μg/ml up to 0.5 μg/ml. A separate, identical set of wells containing the various anti-human LL-12 mAbs and recombinant LL-2 was prepared to determine the effects of the anti-human LL-12 mAbs on EL-2-stimulated proliferation as a measure of inhibitory specificity. A standard dose-response curve ranging from 250 pg or 500 pg per well human or monkey LL-12, respectively, down to 0 pg without added antibodies was also included to determine LL-12- responsiveness. Plates containing mixtures of cytokines and antibodies were incubated for 30 minutes at 37°C, and then 50 μl aliquots of cell suspension were added to the wells. The culture plates were maintained at 37°C in a humidified atmosphere of 5% CO2 in air for 48 hours prior to ^H-thymidine pulsing. Fifty μl of 10 μCi/ml ^H-thymidine (diluted in supplemented media with 5% FCS in lieu of 5% human AB serum) were added to each well. After incubation for an additional 6 hr at 37° C, the well contents were harvested onto glass fiber filters via a cell harvester, and ^H-thymidine incorporation into cellular DNA was measured by use of a liquid scintillation counter. Values shown in Figs. 3 and 4 are the means of triplicate wells. EXAMPLE 12 Inhibition of Cytokine-Stimulated PHA-Activated Lymphoblast Proliferation by Monoclonal Anti-Human IL-12 Antibodies Proliferation of PHA-activated human lymphoblasts stimulated with 0.25 ng/ml LL-12 was inhibited in a dose-dependent fashion by antibodies 5F2, 16F2, 16G2, and 20E11 (Fig. 3). The potencies of these anti-human antibodies, defined as the concentration that produces 50% of maximal inhibition (IC 50 ) of 0.25 ng/ml LL- 12-stimulated proliferation, are 0.03 μg/ml for 5F2, 0.01 μg/ml for 16F2, 0.01 μg/ml for 16G2, and 0.01 μg/ml for 20E11. The maximal (9440 cpm) and background (1480 cpm) levels of lymphoblast proliferation are represented by the horizontal dotted lines at the upper and lower ends of the plots, respectively. As shown in Fig. 3, the 5F2, 16F2, 16G2, and 20E11 antibodies were able to inhibit human LL-12 stimulated PHA activated lymphoblast proliferation by at least 90%. In contrast, as also shown in Fig. 3, the previously identified anti-human LL-12 p75- specific antibody 20C2 (Chizzonite et al., Cytokine, 6: A82a (1994)) is not able to substantially inhibit human LL-12 bioactivity. In addition, as shown in Fig. 4, 5F2, 16F2, 16G2, and 20E11 potently inhibited proliferation of PHA-activated human lymphoblasts stimulated with 0.5 ng/ml rhesus monkey LL-12, with a similar IC50 to that seen with human LL-12- stimulated proliferation. In contrast, 20C2 has only a minimal inhibitory effect on rhesus monkey LL-12-stimulated proliferation. Therefore, the antibodies 5F2, 16F2, 16G2, and 20E11 appear to exhibit good cross-reactivity to rhesus monkey LL-12, whereas the cross-reactivity of 20C2 is much less. None of these monoclonal antibodies inhibited LL-2-induced proliferation, demonstrating that their effect on LL-12-stimulated proliferation was specific for LL-12 and was not due to a general inhibition of cell proliferation. EXAMPLE 13 Interferon-γ Synthesis Assay Interferon-γ (IFN-γ) synthesis was induced using Day 4 PHA-activated human lymphoblasts produced as described above. The medium used was a 1:1 mixture of RPMI 1640 and Dulbecco's modified Eagle's medium supplemented as described above for preparation of natural human LL-12 and containing, in addition, 5% heat-inactivated (56°C, 30 min) fetal bovine serum (Hyclone, Logan, UT, USA) in lieu of human AB serum. Duplicate 1 ml cultures were set up in the wells of 24-well tissue culture plates (Costar). To each well was added 5 x 10^ PHA- activated lymphoblasts, 0.25 ng/ml purified natural human LL-12, 20 units/ml recombinant human LL-2, 1 ng/ml recombinant human LL-lβ (provided by Dr. R. Chizzonite, Hoffmann-La Roche), and the indicated concentrations of anti-human LL-12 antibodies. Initially, all reagents except the lymphoblasts were added to the wells and incubated at 37°C for 30 min, followed by the addition of the lymphoblasts. The cultures were then incubated for 24 hr at 37°C in a humidified atmosphere of 5% CO2 in air. At the end of this time, the culture supernatant fluids were harvested by centrifugation and assayed for their content of LFN-γ by use of an ELISA. The amount of IFN-γ produced in cultures containing lymphoblasts with LL-2 + LL-1 but no LL-12 was always less than 15% and usually less than 5% of that produced in cultures containing 0.25 ng/ml LL-12 in addition to LL-2 + LL-1. The ELISA for measuring human EFN-γ used monoclonal anti-human IFN-γ antibodies from Endogen (Woburn, MA). Nunc EIA plates (Fisher) were coated overnight at 4°C with 100 μl/well of 1 μg/ml anti-human EFN-γ (Endogen #M- 700A) in coating buffer (0.015 M Na CO 3 + 0.035 M NaHCO 3 in distilled water, pH 9.6). The following morning, the coating buffer was flicked out of the wells, and the wells were blocked by addition of 200 μl/well of Dulbecco's phosphate- buffered saline (D-PBS; Fisher) containing 1% bovine serum albumin (Sigma). After incubation for 1 hr at room temperature, the plates were washed with D-PBS containing 0.05% tween 20 (Sigma), and 100 μl aliquots of recombinant human LFN-γ standard (Endogen) or culture supernatants diluted in assay buffer (D-PBS + 0.5% bovine serum albumin + 0.05% tween 20) were added to the wells. The plates were then incubated for 2 hours at room temperature with shaking. Following this, the plates were again washed, and each well received 100 μl of 300 ng/ml biotinylated anti-human IFN-γ (Endogen #M-701-B) in assay buffer. The plates were incubated for 1 hr at 37°C, followed by washing. One hundred μl aliquots of streptavidin-peroxidase (Sigma) diluted 1:1000 in assay buffer were then added to each well, and the plates were incubated for 30 min at 37°C. The plates were again washed and then developed by addition of 100 μl aliquots of a 1:1 mix of TMB Peroxidase Substrate and Peroxidase B Solution (Kirkegaard & Perry Laboratories, Gaithersburg, MD, USA). The reaction was stopped after -12 min by addition of 50 μl/well of 1 M H 3 PO4, and the absorbance was read at 450 nm with subtraction of background at 650 nm. EXAMPLE 14 Inhibition of Cytokine-Stimulated Interferon-γ Production by Monoclonal Anti-Human IL-12 Antibodies Production of IFN-γ by PHA-activated human lymphoblasts stimulated with 0.25 ng/ml human LL-12 was inhibited in a dose-dependent fashion by antibodies 5F2, 16F2, 16G2, and 20E11 (Fig. 5). The potencies of these anti-human antibodies, defined as the concentration that produces 50% of maximal inhibition (IC 50 ) of 0.25 ng/ml human LL-12-stimulated LFN-γ production, are 0.02 μg/ml for 5F2, 0.02 μg/ml for 16F2, 0.01 μg/ml for 16G2, and 0.02 μg/ml for 20E11. These anti-human heterodimer specific LL-12 antibodies were able to inhibit greater than 90% of EL-12-stimulated IFN-γ production when used at 0.5 μg/ml. In contrast, the previously identified anti-human LL-12 p75-specific antibody 20C2 (Chizzonite et al., Cytokine, 6: A82a (1994)) is less potent and is unable to inhibit LL-12- stimulated LFN-γ production by more than 65% at concentrations less than or equal to 0.5 μg/ml. EX AMPLE 15 Sequence Analysis of the Genes Encoding the Variable Region of the Antibody Heavy Chains Present in the Anti-Human IL-12 Antibody-Producing Hybridoma Cell Lines Total RNA was extracted from hybridoma cells using the Ultraspec RNA isolation system following the manufacturer's protocol (Biotecx, Houston, TX, USA). First strand cDNA was synthesized from 10 μg of total RNA and oligo-dT primers in a 20 μl volume. A 4 μl aliquot of the cDNA reaction mix was used as template for the PCR amplification of the mouse IgG heavy chain variable region using primers that were designed according to the sequence information of framework 1 and 4 as reported by Dattamajumdar et al. (A.K. Dattamajumdar et al., Immunogenetics 43:141-151 (1996)). A 30-cycle PCR reaction was performed using an annealing temperature of 50° C. The entire PCR reaction was phenol extracted, ethanol precipitated, and run on a 1% lo-melt agarose gel to isolate the amplicon. The DNA fragment was excised from the gel, melted at 70° C, and 5 μl was reamplified in a 30-cycle PCR reaction to generate more material. The reamplified amplicon was gel purified and sequenced using a flourescence-based S anger method of sequencing with an Applied Biosystems Incorporated automated sequencer. EXAMPLE 16 Nucleotide and Deduced Amino Acid Sequences of the Variable Region of the Monoclonal Anti-Human IL-12 Antibody Heavy Chains The nucleotide sequences of a portion of the variable region of the immunoglobulin heavy chain gene encompassing framework region (FR) 1, complementarity determining region (CDR) 1, FR2, CDR2, FR3, CDR3, and FR4 of IL-12 antibodies produced by hybridoma cell lines HLL-12F3-16G2 and HLL- 12F3-20E11 and the deduced amino acid sequences thereof are shown in Fig. 6 and Fig. 7, respectively. The CDR sequences are underlined. Comparison of available sequence information showed that the heavy chains of antibodies produced by hybridomas HLL-12F3-16G2 and HLL-12F3-20E11 exhibit 94% homology at the DNA level and 93% similarity at the amino acid level. American l pe Culture Collection 12301 Pir lawn Drive • Rockvllle, MD 20852 USA • Telephone: 301-231-5519 or 131-5532 • FAX: 30I-S16- 366 BUDAPEST TREATY ON THE INTERNATIONAL RECOGNITION OF THE DEPOSIT OF MICROORGANISMS FOR THE PURPOSES OF PATENT PROCEDURE INTERN A TIONAL FORM RECEIPT IN THE CASE OF AN ORIGINAL DEPOSIT ISSUED PURSUANT TO RULE 7.3 AND VIABILITY STATEMENT ISSUED PURSUANT TO RULE 10 2 To: (Name and Address of Depositor or Attorney) Hoffmann La-Roche Inc. Attn: Dennis Loh, M.D. 340 Kingsland Street Nutley, NJ 0701 1 Deposited on Behalf of: Hoffmann La-Roche Inc. Identification Reference by Depositor: ATCC Designation Hybridoma cell line HIL-12F3-5F2 HB- 12446 Hybridoma cell line HIL-12F3-16F2 HB-12447 Hybridoma cell line HIL-12F3-20E1 1 HB-12448 Hybridoma cell line HIL-12F3-16G2 HB-12449 The deposits were accompanied by: a scientific description _a proposed taxonomic description indicated above. The deposits were received December 1 1 , 1997 by this International Depository Authority and have been accepted . AT YOUR REQUEST: X_ We will inform you of requests for the strains for 30 years The strains will be made available if a patent office signatory to the Budapest Treaty certifies one' s right to receive, or if a U.S. Patent is issued citing the strains, and ATCC is instructed by theJUnited States Patent & Trademark Office or the depositor to release said strains. If the cultures should die or be destroyed during the effective term of the deposit, it shall be your responsibility to replace them with living cultures of the same The strains will be maintained for a period of at least 30 years from date of deposit, or five years after the most recent request for a sample, whichever is longer. The United States and many other countries are signatory to the Budapest Treaty. The viability of the cultures cited above was tested December 1 8 1 997 On that date the cultures were viable International Depository Authority: American Type Culture Collection, Rockvihe, Md 20S52 USA Date: December 1 9 1 997 cc: Briana Buchholz (Ref. Docket CD 1048P)

Claims: Claims 1. An antibody to the human LL-12 p75 heterodimer which consists of a p35 subunit and a p40 subunit wherein said antibody (a) immunologically reacts with an epitope presented by the p75 heterodimer of human LL-12, but is not immunologically reactive with any epitope presented by said p40 subunit; and (b) is produced from a mammal, preferably a mouse which is deficient in the gene encoding said p35 subunit or the p40 subunit of LL-12. 2. A monoclonal antibody to human LL-12 which consists of a p35 subunit and a p40 subunit forming a p75 heterodimer, wherein said monoclonal antibody (a) immunologically reacts with an epitope presented by the p75 heterodimer of human LL-12, but is not immunologically reactive with any epitope presented by said p40 subunit; and (b) neutralizes at least about 90% of the bioactivity of human LL-12. 3. The antibody of claim 2, wherein the antibody neutralizes at least about 90% bioactivity of human LL-12 by inhibiting LL-12 stimulated PHA-activated human lymphoblast proliferation wherein the concentration of said antibody is 0.5 μg/ml and the concentration of said human LL-12 is 0.25 ng/ml. 4. The antibody of claim 2, wherein the antibody neutralizes at least about 90% bioactivity of human LL-12 by inhibiting LL-12 stimulated LFN-γ production wherein the concentration of the antibody is 0.5 μg/ml and the concentration of said human LL-12 is 0.25 ng/ml. 5. The antibody of any one of claims 1 to 4, wherein the antibody cross reacts with rhesus monkey LL-12. 6. The antibody of any one of claims 1 to 5, wherein the antibody is produced from a cell line of the mouse. 7. The antibody of any one of claims 1 to 6, wherein the antibody is a monoclonal antibody. 8. The antibody of any one of claims 1 to 7, wherein the antibody is produced by a hybridoma, specifically a hydridoma having ATCC designation number HB-12446, HB-12447, HB-12448 or HB-12449. 9. The antibody of any one of claims 1 to 8, wherein the antibody is humanized . 10. A hybridoma that produces an antibody as claimed in any one of claims 1 to 9. 11. A pharmaceutical composition comprising at least an antibody as claimed in any one of claims 1 to 9. 12. A method for producing an antibody that selectively immunologically reacts with the human LL-12 p75 heterodimer which consists of a p35 subunit and a p40 subunit, comprising the steps of: (a) immunizing a mammal deficient in a gene encoding said p35 subunit or said p40 subunit with the human LL-12 p75 heterodimer to produce antibodies; (b) obtaining antibodies from the immunized mammal; (c) screening said antibodies for their ability to selectively bind an epitope presented by the p75 heterodimer to obtain said selectively binding antibody. 13. A method for producing a monoclonal antibody that selectively immunologically reacts with the human LL-12 p75 heterodimer which consists of a p35 subunit and a p40 subunit, comprising the steps of: (a) immunizing a mammal deficient in a gene encoding said p35 subunit or said p40 subunit with the human IL-12 p75 heterodimer to produce antibodies; (b) harvesting antibody producing cells from the immunized mammal; (c) forming a monoclonal antibody producing hybridoma from said cells and obtaining said monoclonal antibody; (d) screening said monclonal antibody produced by said hybridoma for the ability to selectively bind to an epitope presented by the p75 heterodimer to obtain said selectively binding monoclonal antibody. 14. The method of claim 13, wherein the antibodies produced from the hybridoma are further screened and selected for their ability to cross react with rhesus monkey LL-12. 15. The antibody as claimed in any one of claims 1 to 9 whenever produced by a process as claimed in any one of claims 12 to 14 or a process comprising a process as claimed in any one of claims 12 to 14. 16. The antibody as claimed in any one of claims 1 to 9 as a therapeutically active agent. 17. Use of any of the antibodies claimed in any one of claims 1 to 9 for the preparation of a medicament for the controlling of diseases with pathologies that are mediated through immune mechanisms, particularly, diseases associated with increased LL-12 bioactivity that results in aberrant Thl-type helper cell activity like autoimmune disorders, such as, for example, multiple sclerosis, rheumatoid arthritis, autoimmune diabetes mellitus, and inflammatory bowel disease (LBD) including Crohn's disease and ulcerative colitis. 18. The invention as hereinbefore described. *#*

Inventors: GATELY MAURCIE KENT, PRESKY DAVID HOWARD, GATELY, MAURCIE, KENT, PRESKY, DAVID, HOWARD
Applicants: HOFFMANN LA ROCHE, F.HOFFMANN-LA ROCHE AG
Application year: 1999
Main classification: C07K16
IPC codes: A61K39, A61P1, A61P3, A61P19, A61P25, A61P29, A61P37, C07K16, C12N5, C12P21