Identification and immunogenic properties of an 80-kDa surface antigen on a drug-treated tumor variant: relationship to MuLV gp70

Highly immunogenic tumor variants are generated by in vitro or in vivo treatment of L5178Y murine lymphoma cells with triazene derivatives. Most of these variants express new transplantation antigens which are not present on the original L5178Y tumor cells. In this study, a polyclonal syngeneic antiserum raised to one such variant (L5178Y/DTIC) was employed in immunoprecipitation studies of cell surface and metabolically labeled L5178Y/DTIC cells. One- and two-dimensional electrophoretic analyses of the immunoprecipitates detected a surface antigen of approximately 80 kDa. Additionally, a 45-kDa component was detected in the lysate of [35S]methionine-labeled cells. Anti-xenotropic MuLV gp70 serum precipitated material whose electrophoretic pattern was similar to that of the 80-kDa surface antigen. Sequential immunoprecipitation analysis revealed that the molecules reactive with the variant-specific antiserum were removed by the anti-xenotropic gp70 antibodies, whereas immunodepletion was only partial when the cell extract was first treated with the variant-specific antibodies. After Western blotting, the 80- and 45-kDa antigens precipitated by the variant-specific antibodies were injected intrasplenically into recipient mice. Only the animals sensitized with the 80-kDa antigen developed specific immunity to L5178Y/DTIC cells in that they displayed an increased frequency in CTL precursors (CTLp) to the variant cells. Sera from mice sensitized to the 80-kDa protein specifically inhibited the development of a primary CTL response to L5178Y/DTIC cells.