Abstract
Mixtures of lymph node and spleen cells from normal (untreated) BALB/c mice and from BALB/c mice whose syngeneic tumors had been excised 7–28 days previously (“tumor‐excised mice”), were sensitized in vitro by cultivation for 9 days with cells from syngeneic, methylcholanthrene‐induced sarcomas. The in vitro‐ sensitized lymphoid cells were tested in a 36‐h microcytotoxicity assay for reactivity against target cells carrying the sensitizing tumor antigens, as well as against control target cells lacking these antigens. After co‐cultivation with tumor cells, lymphoid cells from both normal and tumor‐excised mice were cytotoxic to tumor cells carrying the sensitizing antigens. The cytotoxicity was generally specific, and occurred at low effector: target cell ratios (in some experiments down to 1:1). When lymphoid cells from tumor‐excised mice were exposed in vitro for 9 days to cells carrying the same antigens as those which were originally present on the surgically excised tumors, the effector cells obtained gave a dose‐dependent cytotoxic response suggestive of a linear relationship. When lymphoid cells from normal mice were similarly sensitized for 9 days, specifically cytotoxic lymphoid cells were generated but no linear dose‐dependent response was detected.