Experimental study on merits and demerits of splenectomy in tumor bearers

Immunologic merits and demerits of splenectomy were studied using a rat's experimental tumor. When splenectomy was done on day - 14, 2, or 14 of tumor inoculation, subsequent tumor growth was inhibited, but when it was done on day 7, tumor enhancement was observed. On day 2, cpm values of phytohemagglutinin (PHA)-induced blastogenesis of splenocytes was lower than in normal rats, on day 7 they significantly increased as compared with day 2, and on day 14 they significantly decreased as compared with day 7. Stimulation index (SI) ratio of PHA-induced blastogenesis and natural cell-mediated killing (NK) activity were also investigated using splenocytes, thymocytes, and peripheral lymphocytes. The results indicated that immunological competency of splenocytes of tumor bearers was reduced in the early, late, and final tumor-bearing periods, while it was increased in the middle tumor-bearing period. Tumor growth following splenectomy was considered to be controlled by these changes in immunological competency of splenocytes.