| Abstract: | The effector mechanism of immune spleen cells against syngeneic TMT mammary tumor cells was analyzed in vitro. C3H/He mice were first inoculated with TMT tumor cells, and then the tumors were x-irradiated with 2000 rad 1 wk after the inoculation. Spleen cells from these treated mice inhibited the growth of tumor cells in vitro when assessed by (3H)-TdR incorporation by tumor cells (cytostatic activity). The same spleen cells did not have any cytotoxic activity on TMT tumor cells detected by a 51Cr-release assay. The cytostatic activity was mediated by Lyt-1+23- T cells. The purified T cells alone could not inhibit the growth of tumor cells, but accessory cells were required for the induction of cytostatic T cell activity. The accessory cells were Ia-positive, macrophage-like adherent cells. Furthermore, both T cells and macrophages were also required for the inhibition of tumor growth even after the spleen cells were activated in vitro. These results suggest T cells and macrophages play an important role in the effector mechanism against TMT mammary tumor cells. The mechanism of cytostasis by T cells and macrophages was discussed from the standpoint of the cellular interaction. |
