H-2 control of the cytotoxic antibody response against a newly defined MuLV-related cell-surface antigen: G(B10.A)

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Abstract
H-2-congeneic C57BL mice with milk transmission of B-tropic murine leukemia virus (V+ mice) have a much higher lymphoma incidence than the same strains without milk-transmitted virus (V—mice). Gene(s) within the major histocompatibility complex (H-2) influence virus titers, lymphoma incidence, lymphoma type and the anti-MuLV envelope antibody response. In this paper, we report that the prevalence of cytotoxic antibodies to virus-induced lymphomas is also regulated by the H-2 complex. Milk transmission of MuLV resulted in the formation of cytotoxic antibodies against primary virus-induced C57BL lymphomas. These antibodies detect an antigen that is also present on the RADAI tumor-cell line, and on normal spleen cells of young adult B10.A (H-2a) mice of both V+ and V- sublines, but not on spleen cells of young adult B10 (H-2b) mice of either subline. These cytotoxic antibodies were detected in the sera of B10V+ and B10.A(5R)V+ animals, but not in the sera of B10.AV+ mice. This indicates that the prevalence of these antibodies is controlled by a gene in the K-and/or I-A region of the H-2 complex. The presence of these cytotoxic antibodies in serum is recessively inherited. The specificity of the cytotoxic antibodies was investigated with a standard panel of transplantable tumor-cell lines. Of these, only the RADAI cells expressed the target antigen in direct cytotoxicity tests and by absorption. The ability of B10V+ sera to lyse the B10.AV+ and RADAI tumor cells is ascribed to antibody activity against a new MuLV-related cell-surface protein: G(B10.A). Immunochemical analysis and absorption experiments with different types of purified MuLV and MuLV-infected cell lines indicate that the cytotoxic antibodies belong to low-avidity IgM antibodies that are directed to MuLV.