Non-specific cytotoxic cells generated in vitro in response to a weakly immunogenic murine adenocarcinoma. In vivo...

Tumor 85 adenocarcinoma cells, which are very weakly immunogenic for C3H/HeN (C3H) mice, provide a model tumor system for studying the parameters of induction of a cell-mediated immune response which does not appear to be a traditional cytotoxic T-cell or NK-cell response. Mice pre-immunized with irradiated tumor 85 cells are protected about 50% of the time from a challenge of viable tumor 85 cells although it is never possible to protect 100% of the immunized mice. Optimal protection is observed in mice immunized with 10(6) irradiated tumor 85 cells 14 days prior to challenge. Protection is also observed if mice are immunized with Protection is also observed if mice are immunized with 3H or C3HfeB/HeN (C3Hf) tumors originally induced by the same carcinogen as that used to induce tumor 85. The injection of carrageenan 1 h before challenge completely reverses the protection observed in immunized mice and and tumors grow faster in carrageenan-treated immunized mice than in normal mice. Two populations of cells obtained from cultures of spleen cells stimulated by tumor 85 cells appear to prevent tumor growth in vivo. One population, which is cytotoxic for tumor 85 cells in vitro, is nylon-wool-adherent and expresses Thy 1.2. The second population, which is not observed to be cytotoxic in a 51Cr release assay, is phagocytic.