Peritoneal cell populations during tumour injection.

The response of peritoneal cells to the SL2 lymphoma was studied in immunized and non-immunized mice to elucidate further the cellular events that lead to tumour rejection in an allogeneic and a syngeneic tumour system. Anti-tumor immunity was induced by intraperitoneal injection of normal, irradiated or mitomycin-C treated tumour cells. Four different immunization schedules were tested. The response of the peritoneal cells was investigated by studying the peritoneal cell population kinetics (appearance and/or disappearance of various cell types e.g. mononuclear phagocytes, lymphocytes, PMNS and mast cells). Total cell counts were done using phase contrast microscopy, differential cell counts were done on cytocentrifuge slides, stained with May Grünwald-Giemsa. The activity of the lysosomal enzyme beta-glucuronidase present in mononuclear phagocytes was also studied. The results indicated that the composition and morphology of the cellular fraction of the peritoneal exudate changes quite dramatically during tumour rejection. Especially the beta-glucuronidase activity of the mononuclear phagocytes line varies significantly. The observed changes in the cellular population depended upon the dose of tumour cells injected i.p. No significant differences were observed between the peritoneal cell populations of mice grafted i.p. with irradiated or with mitomycin-C treated tumour cells. On the other hand when mice previously immunized with three injections with 10 irradiated or mitomycin-C treated tumour cells were challenged i.p. with various doses of tumour cells, the immune potency against the tumour is greater after previous immunization with irradiated SL2 cells than after immunization with mitomycin-C treated tumour cells.