T cell-dependent nonspecific cytotoxicity induced by culture of mouse spleen cells against natural killer-insensitive tumor cells.

Normal mouse spleen cells exhibited nonspecific cytotoxicity against MM2 and other NK-insensitive mouse ascites tumor cells after culture for 3 or 4 days in vitro in the presence of heat-inactivated foetal calf serum and 5 X 10(-5) M 2-mercapthoethanol. The cytotoxicity was assayed by 51Cr-release during 18 hr incubation. Culture of spleen cells from C3H/He or C57BL/6 mice resulted in strong cytotoxicity, while cytotoxicity did not appear or appeared only weakly during culture of spleen cells from Balb/c, DDD, DBA/2 or athymic mice. High activity was observed when spleen cells from aged mice were used. The effector cells which lysed MM2 cells seemed glass dish non-adherent, Sephadex G-10 adherent, nylon wool adherent, and Thy 1.2 positive cells. The induction of cytotoxicity was inhibited by adding cytosine arabinoside to the culture medium. Mouse serum was also inhibitory. Restriction specificity between the effector and the targets was not observed for the lytic reaction. By cold target competition experiments, it was shown that the effector cells recognize cell surface structures commonly present on the surface of wide range of tumor cells which are unrelated with respect to tumor specific antigenicity.