[Changes in immunological function of spleen in rats implanted with N-methyl-N'-nitro-N-nitrosoguanidine-induced...

We evaluated killer cell activity and suppressor cell activity as the indicators of immunological function of spleen cells in rats implanted with N-methyl-N'-nitro-N-nitrosoguanidine-induced cancer. The effect of splenectomy on tumor growth was also investigated. Splenectomy was performed 2 (early stage of tumor growth), 5 (intermediate stage), or 8 weeks (late stage) after tumor implantation. The mean survival time of rats splenectomized at the early or intermediate stage of tumor growth was shorter than that of sham-operated rats, while that of rats splenectomized at the late stage was longer than controls. Natural killer (NK) and Cytotoxic T lymphocyte (CTL) activity of spleen lymphocytes of tumor-bearing rats were increased during the intermediate stage of tumor growth and then were declined during the late stage, while suppressor cell activity showed progressive increase after tumor implantation. The results of Winn assay showed that most of the splenic effector cells during the intermediate stage were T-lymphocytes, and some were NK cells. Furthermore suppressor macrophages and suppressor T-lymphocytes were increased in spleen lymphocytes of rats in the late stage of tumor growth. These results suggest that preservation of the spleen may be beneficial in the treatment of gastric cancer at the early and intermediate stage but that splenectomy is necessary for the advanced stage of cancer.