EFFECT OF SPLENECTOMY ON TUMOR GROWTH, SURVIVAL, AND BLOOD LYMPHOCYTE SUBSETS IN TUMOR BEARING MICE

The spleen is the largest peripheral lymphoid tissue and plays an important role as one of the immune associated organs, but the effect of splenectomy in cancer therapy remains obscure. The tumor growth, host survival, and the change of T-lymphocyte subsets (Lyt2⁺, L3 T4⁺) in blood and spleen were studied using tumor bearing mice (Colon 26 bearing BALB/c mice) to investigate the effect of splenectomy, and the following results were obtained. 1. In cotrol group (CONT), the subcutaneous mass appeared macroscopically in the 8th day after tumor inoculation (Colon 26,2×10⁴), and started to death on the 30th day. Lyt2⁺ and L3 T4⁺ ratio of spleen elevated to the highest level on the 6th day and returned to the same level with tumor growth, on the other hand, Lyt2⁺ ratio of blood kept constant regardless of tumor growth, and L3 T4⁺ ratio dropped to the lowest level on the 9th day, and returned to the same level with tumor growth. 2. When splenectomy was done on the 5th day after tumor inoculation (SPN 5 ; early phase), Lyt2⁺ ratio of blood was significantly decreased (p<0.05) as compared with other groups, and subsequent enhancement of tumor growth and the shortening of survival period were observed (p<0.05). 3. On the 10th day after tumor inoculation (SPN 10 ; middle phase), Lyt2⁺ ratio of blood was significantly elevated (p