Role of delayed hypersensitivity and cytostatic macrophages in the rejection of an allo-transplantable murine tumor.

Growth of an allo-transplantable tumor, sarcoma-180, was suppressed in ICR mice immunized with mitomycin C-treated tumor cells in Hanks' solution or heat-killed tumor cells mixed with complete Freund's adjuvant 7 days before subcutaneous inoculation of tumor cells. In those mice, cytotoxic lymphocytes were not detected in spleen, lymph node or peritoneal exudate cells before or after tumor inoculation. The activities of antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity were not found in sera. Cytostatic activity was detected in peritoneal glass-adherent cells, but not in glass-nonadherent cells. Such an activity was also conferred on normal peritoneal glass-adherent cells by incubation with the culture supernatant of lymph node cells from preimmune mice and tumor cells. Cytostatic macrophages mediated by lymphokine-producing lymphocytes may be at least one of the main effector mechanisms in resistance against such an allo-transplantable tumor line.