Inhibition of cell-mediated cytotoxicity against tumor-associated antigens by suppressor lymph node cells from mice bearing methylcholanthrene-induced sarcomas.

Suppression of cell-mediated cytotoxicity directed against tumor-associated membrane antigens of methylcholanthrene (MC)-induced sarcomas by lymph node cells (LNC) from tumor-bearing mice was examined by inhibition of the 3H-thymidine incorporation assay. Normal LNC from B10 mice had been sensitized in vitro by 6-day cultivation on layers of irradiated syngeneic sarcoma cells and the effect of the generated cytotoxic lymphocytes was then inhibited by the admixture of suppressor cells present in lymph nodes of tumor-bearing mice. Suppressor cells were detected in lymph nodes from 7 of 16 (44 per cent) individually examined tumor bearers when LNC were added to cytotoxic lymphocytes which had been presensitized in vitro. When the experimental schedule was reverted and the tumor bearers' LNC were admixed to the normal LNC prior to the in vitro sensitization so that they were present in the population of the effector cells throughout the period of sensitization, the suppressor effect was detected in only 1 of 9 (11 per cent) tumor-bearers. The suppressive effect of tumor bearers' LNC was found to be nonspecific, being elicited not only by LNC derived from bearers of the sensitizing tumor, but also by LNC from bearers of an unrelated, immunologically noncross-reacting MC-induced sarcoma.