Augmentation of Antitumor Cytotoxicity in MOPC-315Tumor Bearer Spleen Cells by Depletion of Glass-adherent Cells Prior to in Vitro

Noncytotoxic, MOPC-315 tumor bearer spleen cells were converted to a cytotoxic state by in vitro activation with MOPC-315 stimulatortumor cells.The levelof in vitro cytotoxicity exhibited by activated spleen cells from mice bearing small tumors was similar to that of activated spleen cells from normal mice while that exhibited by activated spleen cells from mice beaming large tumors was much lower. The decrease in the level of in vitro antitumor cytotoxicity observed in activated tumor bearer spleen cells during progressive tumor growth correlated with an in crease in the percentage of macrophages in the spleen. Depletion of glass-adherent cells from the spleens of tumor beaming mice included the removal of most macmophages and resulted in the expression of cytotoxicity upon culture and in the augmentation of cytotoxicity upon activation. Still, unactivated or MOPC-315-activated, nonadherent, tu mombearer spleen cells did not lyse allogeneic EL4 leuke mia or syngeneic normal BALB/c target cells. The in vitro cytotoxic activity exhibited by activated, nonadherent, tu mombearer spleen cells against MOPC-315 target cells was at least 10-fold greater than that exhibited by activated normal spleen cells or activated, unfractionated, tumor bearer spleen cells. Furthermore, activated nonadherent, tumor bearer spleen cells were also superior to activated, unfractionated, tumor bearer spleen cells in mediating in vivo antitumor activity in the local adoptive transfer assay. Thus, activated, nonadhement, tumor bearer spleen cells might be useful in immunotherapeutic regimens requiring histocompatibie cells with augmented antitumor cytotoxic