Mechanisms of Tumor Homograft Rejection. II. Studies on the Mechanism of Rejection of Sarcoma I Ascites Tumor in the C57BL/Ks Mouse

Our previous observations, that peritoneal macro phages from C57BL/Ks mice immunized with Sarcoma I ascites tumor have a strong and specific affinity for the tumor cells, were confirmed. Unsuccessful attempts were made to increase the low rate of phagocytosis of Sarcoma I, which characterizes its natural history in the C57BLlKs mouse, by in vitro treatment with immune serum and with immune serum plus complement before injection into the peritoneum of tumor-immune animals. Whereas the Ruorescent antibody method failed to demonstrate antibody on Sarcoma I cells during the rejection period, its presence on the cells was indicated by pronounced cytotoxic effects induced with rabbit complement both in vitro and in vivo. The intraperitoneal injection of immune serum on the 5th, 6th, and 7th days of tumor did not injure tumor cells. The intraperitoneal injection of rabbit complement produced limited injury of tumor cells when given on the 4th and 5th days of tumor and marked injury of tumor cells when given on the 6th, 7th, 8th, 9th, and 10th days of tumor. In contrast to the failure of either immune serum or complement to produce marked injury of tumor cells when given on the 5th day of tumor, combined treatment with both antibody and complement at this interval resulted in a marked increase in the percent of nonviable tumor cells. Despite the cytotoxic effects of antibody demonstrable with rabbit complement, the treatment of tumor-bearing animals with rabbit complement did not significantly alter the time of tumor rejection.