Evolution of cell‐mediated antitumor immunity in mice bearing a syngeneic chemically induced tumor. Influence of tumor growth, surgical removal and treatment with irradiated tumor cells

Abstract

Abstract The evolution of the specific cell‐mediated immune status was studied in C57BL/6 mice bearing a chemically induced syngeneic sarcoma, the TBL CL2 tumor. Peritoneal cells (PC) as the source of immunocompetent cells were repeatedly harvested from the same groups of mice checked in the in vitro colony growth inhibition tests (CGI) against target TBL CL2 cells. Confirming our data previously reported from studies with other tumor‐host models, a characteristic evolution of the cell‐mediated immune status was observed. Ten days after tumor inoculation, the PC from the tumor‐bearing mice strongly inhibited the tumor target cells in the CGI test. This reactivity was, however, soon followed by an “eclipse” state of PC. This state continued, whenever checked, until the tumor‐bearer's death. On the contrary, surgical removal of the tumor 6 weeks after inoculation led to a reappearance of PC reactivity within about 2 months. This period was clearly shortened in animals receiving a post‐operative injection of irradiated cells of the TBL CL2 tumor. An in vivo study of tumor‐graft rejection revealed a fair degree of parallelism with the CGI tests: the tumor graft was rejected in animals bearing the first tumor for 10 days and having activated PC; the tumor graft was not rejected in animals bearing huge tumors and having PC in the “eclipsed” state.