Cooperation and Cell-Mediated Cytotoxicity as Functions of two Subsets of T Cells

Abstract

After stimulation of mice with alloantigens we compared the ability of their spleen cells to effect cell-mediated cytotoxicity and to assist in the triggering of bone marrow-derived lymphocytes. We did this using the DBA/2 mastocytoma, P815, as allogeneic immunogen on the one hand and as target for cytotoxicity and carrier for hapten on the other. Spleen cells from animals immunized with either low doses of irradiated or formaldehyde-treated P815 cells exhibit cooperating activity but not cytotoxic activity. In addition, we show that spleen cells from C57BL/6 mice immunized with P815 do contain cytotoxic thymus-derived (T) lymphocytes but are unable to trigger bone marrow-derived cells for a hapten response in vitro to hapten-coupled P815 antigen. That there may be some helper cells in cytotoxic spleens is not excluded, for we show that mixing cytotoxic spleens with those showing helper function blocks the expression of that helper function. Since we show that both functions, helping and killing, are sensitive to anti-θ serum, we conclude that they are carried out by two different subsets of T cells.