We have studied the mechanisms involved in the activation or suppression of the immune response by the tumor cells, which is also dependent on the site of tumor transplantation. AK-5 tumor cells when transplanted s.c. activated peritoneal macrophages through the induction of different cytokines, whereas tumor cells when transplanted i.p. suppressed the activity of macrophages as well as the production of cytokines. Suppression of macrophage function was also observed when they were cocultured with tumor cells in vitro. Our studies suggest the capability of AK-5 tumor in driving the immune response either towards activated status or towards immune suppression, depending on the site of transplantation. Activated macrophages produced free radicals, which were cytotoxic to the tumor cells.
Animals Antigens, Neoplasm