Nonspecific cytotoxic cells induced in vivo and their comparison to culture-induced cytotoxic cells.

Nonspecific cytotoxic cells in peritoneal exudate cells obtained from mice injected with P. acnes and other stimulants were characterized using MM2 ascites mammary carcinoma as target cells which were insensitive to lytic activity of natural killer cells and of activated macrophages. MM2-lytic activity was recovered in nonadherent cells after incubation on glass surface for 1 hr, although it was recovered only partly in nonadherent fraction after extensive adherence. The characteristics of the recovered cells was similar to those of culture-induced, nonspecific cytotoxic cells with respect to target selectivity, enhancement of the activity by serum from tumor-regressor mice, suppression of the activity by fresh spleen cells and adhesiveness to a Sephadex G-10 column. They were different from each other concerning adhesiveness to glass surface during extensive incubation and dependence on T cells for their activity. By newly devised effector competition technique, in which formaldehyde-inactivated effectors competed the activity of nontreated effectors, it was shown that the effectors induced in vivo by P. acnes and culture-induced effectors commonly recognized a target structure on MM2 cells. Possible classification of nonspecifically cytotoxic cells based on recognition structures on their surface is discussed.