Xenogeneic cellular immune responses and the control of microscopic tumor. A model.

Regimens for the generation of a highly cytotoxic xenogeneic response, the mechanism of this response, and its effect on tumor cells were investigated in a rat antimouse tumor system. Fischer 344 rats were immunized with EL-4 lymphoma and the ability of the sensitized rat lymphocytes to suppress the local growth of four different C57BL/6 tumors was evaluated. Optimal sensitization of the rat was achieved using large numbers of viable tumor cells in a primary intraperitoneal immunization. Highly cytotoxic effector cells generated in this xenogeneic setting significantly suppressed the local growth of appropriate tumor targets. Rat T cells appeared to be the sole effector cell and their effect was abrogated by anti-rat immune responses in the host mouse. This rat anti-EL-4 model with allow further investigation into xenogeneic antitumor responses and their possible role in local immunotherapy.