Host-derived antibody-dependent cytotoxic cells within murine tumors

Mouse ascites tumor preparations had strong antibody-dependent cell-mediated cytotoxic (ADCC) activity, whereas cultured tumor cells did not. L5178 lymphoma cells reversibly expressed surface Fc receptors in vivo but not in vitro. Cultured lymphoma cells grown in vivo in diffusion chambers expressed Fc receptors but not ADCC activity. These results suggest that an Fc receptor is not sufficient to endow a cell with ADCC activity. The transplanted ascites tumors L5178 and MOT, an ovarian teratoma, contained about 2-5% host-derived cells, which represents a significant increase in the total number of host-derived peritoneal cells compared to the number of cells found in nontumor-bearing mice. These infiltrating host cells were separated from the ascites tumor cells by velocity sedimentation and by lysis with antibody and complement. In both instances, all the ADCC activity was associated with the host cells, whereas cells, such as killer cells and macrophage;, infiltrate ascites tumors and completely account for the potent ADCC activity associated with ascites tumor preparations.