Abstract
Rous sarcoma virus (RSV)‐transformed fibroblasts from different animal species a serologically detectable virus‐induced non‐virion cell surface antigen (VCSA), whose expression is controlled by the transforming viral srcgene and by a cellular gene. Now, by in vivo immunization, we have found that RSV‐transformed fibroblasts from different mouse strains share a virus‐specific transplantation antigen. In fact, only animals immunized with irradiated syngeneic or allogeneic fibroblasts transformed by RSV, but not animals immunized with cells transformed by different oncogenic agents, rejected a lethal dose of syngeneic RSV‐induced tumor cells. Immunoprecipitation tests with monospecific antisera showed that the expression of this antigen did not correlate with the presence of intracellular viral proteins other than the src gene product pp60^src^. However, hyperimmunization of mice with hamster or quail fibroblasts transformed by RSV, that express a high level of pp60^src^, did not induce transplantation resistance. It is concluded that the expression of both the serologically‐defined VCSA and the transplantation antigen is the result of the interaction of pp60^src^ with host cell gene product(s) rather than the simple exposure of pp60^src^ at the outer cell surface.