ADSORPTION OF SUPPRESSOR CELL-ACTIVITY ON MOUSE MACROPHAGE MONOLAYERS

Suppressor cell activity was high in spleens of C57BL/6 mice sensitized to the allogeneic P-815 mastocytoma. Suppressor cells inhibited proliferation of normal mouse spleen cells in mixed lymphocyte cultures. Preincubation of tumor-allosensitized spleen cells on monolayers of syngeneic or allogeneic macrophages reduced suppressor activity. Preincubation on monolayers of spleen cells did not affect suppressor activity. Suppressor cells could be retrieved from macrophage monolayers used for adsorption. Heat-killed macrophages failed to adsorb out suppressor cell activity. Incubation of tumor-allosensitized spleen cells on syngeneic macrophage monolayers did not reduce cytotoxic cell activity. Removal of suppressor cell activity by macrophage adsorption restored helper activity of tumor-allosensitized spleen cells. Suppressor cell activity could be reduced by contact with macrophages, and an additional role for the macrophage in regulating the immune response to tumors was suggested.