In situ cytotoxic T cells in a methylcholanthrene-induced tumor.

The in situ localization of cytotoxic T-cells was examined in a methylcholanthrene-induced fibrosarcoma. The MCA 2 tumor was initiated in this laboratory and utilized before extensive in vivo passage. Tumor cell suspensions were separated by unit velocity sedimentation. The T cell-enriched tumor-derived fractions and spleen cells from MCA 2-bearing mice were cytotoxic for in vivo isolated MCA 2 and in vitro cultured MCA 2 tumor cells, but not for SAD2 tumor cells. The cytotoxic activity of effector cells isolated from MCA 2 tumors was abrogated by treatment with anti-theta serum plus complement. The significance of cytotoxic T cells with in a progressing tumor is discussed.