Augmentation of cell-mediated cytotoxicity against syngeneic Gross virus-induced lymphoma in rats by phytohemagglutinin and endotoxin.

Normal W/Fu rat spleen cells cultured for 1 day with mitogenic concentrations of phytohemagglutinin (PHA) or with a wide range of concentrations of endotoxin (LPS) exerted cytotoxic activity against the syngeneic Gross virus-induced lymphoma, (C58NT)D, and also against other tumor cells in a 4-hr 51Cr release assay. This activity did not involve release of detectable lymphotoxins, nor did it require the presence of additional mitogen in the media during the cytotoxicity assay. The cytotoxic activity induced by PHA was dependent on the presence of T cells while the activity induced by LPS was not dependent on T cells and appeared to require the presence of macrophages. Both PHA and LPS also augmented the cytotoxic activity of spleen cells immune against (C58NT)D tumor cells. With submitogenic concentrations of PHA, only specific cytotoxicity against (C58NT)D cells was augmented. In contrast, LPS and mitogenic concentrations of PHA caused nonspecific augmentation. Mitogenic concentrations of PHA and LPS also augmented the antibody-dependent cytotoxicity of normal W/Fu rat spleen cells against (C58NT)D cells in the presence of syngeneic anti-serum.