Nonspecific inhibition of in vivo tumor growth by allo-sensitized lymphocytes - requirement of radio-sensitive T-lymphocytes.

In previous papers we demonstrated with the Winn assay the WKA rat spleen cells sensitized to allogeneic tumor (AH-66 from Donryu strain) inhibited in vivo tumor growth of a syngeneic tumor (KMT-17) when early spleen cells (taken one week after the last immunization) were used. For the tumor inhibition by late spleen cells (2 weeks after the last immunization), further addition of inactivated homologous allogeneic cells was required. In the present study we examined with the Winn assay the nature of allo-sensitized spleen cells which nonspecifically inhibit in vivo growth of syngeneic tumors. Tumor inhibitory activity of early spleen cells was decreased by anti-rat T serum treatment. The same was true in tumor inhibition by late spleen cells stimulated with mitomycin-C treated AH-66 cells. Both of early and late spleen cells responsible for tumor inhibition are radio-sensitive, whereas KMT-17 sensitized T cells which specifically inhibited growth of homologous tumor cells belong to radio-resistant subpopulations.