Further studies on cross-immunity among syngeneic tumors in mice

In the present studies employing 3-methylcholanthrene (MCA)-induced sarcomas of C3H/He mice, cross-immunity among syngeneic tumors was markedly demonstrated by immunization with living tumor cells after repeated inoculation of gamma-irradiated (13, 000 rads 60Co) tumor cells. Cross-immunity was also markedly shown in the challenge of the other MCA-induced tumor, which was induced in the same mouse in which the immunizing MCA-induced tumor originated, by repeated immunization with gamma-irradiated tumor cells only. On the contrary, cross-immunity was not observed between tumors induced on different mice by repeated immunization with gamma-irradiated tumor cells only. As the result of the immunization with gamma-irradiated tumor cells only, common antigenicity among syngeneic tumors seems to be hardly demonstrated, and antigenic indiviDuality among animals, in which MCA-induced sarcomas originated, seems to be remarkably demonstrated.