Identification of effector cells for TNFα-mediated cytotoxicity against WEHI164S cells

Abstract WEHI164S cells were found to be very sensitive targets for in vitro killing in a 6-h culture when liver or splenic lymphocytes were used as effector cells in mice. Of particular interest, a limiting cell-dilution analysis showed that effector cells were present in the liver with a high frequency (1/4300). In contrast to YAC-1 cells as NK targets, perforin-based cytotoxicity was not highly associated with WEHI164S killing. The major killer mechanism for WEHI164S targets was TNFα-mediated cytotoxicity. By cell sorting experiments, both NK cells and intermediate T cells (i.e., TCR int cells) were found to contain effector cells against WEHI164S cells. However, the killer mechanisms underlying these effector cells were different. Namely, NK cells killed WEHI164S cells by perforin-based cytotoxicity, TNFα-mediated cytotoxicity, Fas ligand cytotoxicity, and other mechanisms, whereas intermediate T cells did so mainly by TNFα-mediated cytotoxicity. These results suggest that TNFα-mediated cytotoxicity mediated by so-called natural cytotoxic (NC) cells comprised events which were performed by both NK and intermediate T cells using somewhat different killer mechanisms. Intermediate T cells which were present in the liver were able to produce TNFα if there was appropriate stimulation.