Antigenic specificity of benzo[a]pyrene-induced sarcomas

Tumors induced in C3H and C57BL mice by benzopyrene elicited isograft immune reactions to tumor-specific antigens. The antigenicity of primary tumors was higher than that of the same sarcomas after a series of transfers through isologous hosts. Apparently the progressive growth of transplants of primary tumors is determined by the antigenicity of the tumors. Sarcomas that did not take in normal hosts—such as grafts of early transplant generations—grew progressively when transplanted to animals exposed to total-body X irradiation, i.e., in immunologically suppressed animals. The decrease in antigenicity was not associated with a complete loss of the tumor antigens. Tumors that could no longer immunize animals were still susceptible to the immune response elicited by immunogenic grafts of earlier transplant generations. Each of the 2 sarcomas produced in a single animal by 2 simultaneous applications of the carcinogen had distinct antigenic specificity. Tumors produced in a single animal may differ from each other in (a) transplantability, (b) immunogenicity, and (c) antigenic specificity. The exposure of preimmunized animals to X irradiation, followed by test grafting, was most useful for the analysis of antigenic specificity of non-transplantable tumors. Experiments in which sarcomas, originating in C3H, were tested for antigenicity in (C3H × C57BL)F₁ hybrids demonstrated that the lack of manifested immunological reactivity to certain tumors is due to the properties of the tumor cells themselves and not to the recipient animals.