Specific cytotoxic lymphocytes against syngeneic tumors are generated in culture in the presence of syngeneic, but not xenogeneic, serum.

Experiments were performed to test the effect of xenogeneic (fetal calf) serum (FCS) , as compared to syngeneic mouse serum (SMS) on the generation in culture of specific cytotoxic lymphocytes (CL) against syngeneic tumors. Sensitization in FCS against 3LL tumor cells resulted in CL cross-reacting with B-16 tumor cells and vice versa. Anti-syngeneic fibroblast CL also cross-reacted with 3LL. Such cross-reactivities were shown to be derived from CL directed against FCS determinants. In contrast, sensitization in the presence of SMS resulted in CL directed against tumor-specific antigens. Anti-3LL generated in SMS lysed 3LL targets but not B-16, and anti-B-16 lysed B-16 but not 3LL. The two types of CL had two distinct reactivities in vivo. Anti-3LL CL generated in FCS enhanced tumor growth in vivo, whereas anti-3LL CL generated in SMS had an inhibiting effect on the growth of tumor cells. These results indicate that the application of syngeneic serum during in vitro sensitization against syngeneic tumors may open up new possibilities for the analysis of tumor-specific antigens and for eliciting specific immune reactions against such antigens.