The cross-immunity among syngeneic tumor cells which have been irradiated with 60Co

The experiments on the cross-immunity among various 3-methyl-cholanthrene (MCA) sarcoma were carried out using C3H/He mice. When the 60Co irradiated tumor cells were used as an antigen, strong cross-immunity was observed among the two tumors which appeared in an organism, but no cross-immunity was observed among the tumors which appeared in the different organisms. This seemed to indicate that the 60Co irradiation decreases the common antigenicity of live tumors and that it strengthens the differences of the antigenicity among the tumors of individual animals. (Saito, K.)