Effect of sensitized macrophages in transplantable sarcoma in mice: Synergistic effect of hyperimmunized serum, sensitized spleen cells and macrophages in tumor transplantation

Background. Immunosuppression cannot develop tumors by itself. It may induc e tumors under appropriate conditions and may accelerate tumor development which may be reversed by sensitized spleen cells. This study concerns the e ffect of sensitized macrophages in murine-transplantable sarcomas by a comb ination of hyperimmune serum, sensitized spleen cells and macrophages. Methods. The main technique adopted was intraperitoneal (ip) injection of 2 mL of 10% protease peptone broth, followed 2 days later by inoculation int o the peritoneum with 10-mL Hank isotonic solution. The cells from the pool ed peritoneal fluid were tested by dye exclusion test to ascertain the perc entage of live cells, They were tried in whole body-irradiated mice with a combination of immune serum and sensitized spleen cells to ascertain whethe r a suppression of growth of solid tumors could be achieved when subcutaneo usly (sc) administered with the previously mentioned combinations. Results. The addition of immunomacrophages from transplanted tumor-bearing mice significantly suppressed the growth of subcutaneous solid tumors when the number of tumor cells was kept constant. A change in number of immunoma crophages from hyperimmunized mice at a ratio of 4:1 showed a direct relati onship in suppression of tumor growth. Experiments were initiated in which tumor cells were injected sc and peritoneal macrophages were injected eithe r intravenously (iv) or ip. Experiments were then initiated to prove that c ell-to-cell contact is essential for tumor suppression. In experiments in w hich tumor cells were administered sc and macrophages injected either iv or ip, a significant immunosuppressive effect was not shown, thus also indica ting that regardless of which, cell-to-cell contact is an absolutely essent ial factor involved in tumor suppression. A combination of hyperimmune seru m and macrophages was found to act synergistically. Macrophages and hyperim mune serum at a lesser proportion did not suppress tumor growth, Sensitized macrophages and spleen cells together significantly suppressed tumor growt h in a pure isogenic strain of irradiated mice, The sensitized macrophages injected iv prolonged the survival period and retarded tumor growth. Conclusions, Tumor suppression by macrophages was found to be due to its co ntact with tumor cells that enables the effective transfer of immunity, Hyp erimmune serum and other cells (macrophages, spleen lymphocytes) act synerg istically toward each other and prolong the survival period. (C) 2001 IMSS. Published by Elsevier Science Inc.