[Immunological effect of splenectomy in tumor-bearing rat]

Immunologic merit and demerit of splenectomy were studied, using experimental model in rat.

SD rat. Tumor: Metastasizing Rat's Mammary Tumor No. 1 (MRMT-1) originally induced by 3-MC administration to SD rat. Experimental study: Splenectomy was done on day before and after subcutaneous inoculation of 200mg of MRMT-1 at the back of 4 week-old female SD rats. Tumor growth following splenectomy and immunological competency of rat's peripheral lymphocytes, spleen cells and thymus cells was investigated and following results were obtained. When splenectomy was done pre-operatively or on the 2nd or 14th day after tumor inoculation, subsequent tumor growth was inhibited, however, when it was done on the 7th day after the inoculation, tumor enhancement and shortening of survival period were observed. When it was done on the 21st day, tumor growth was almost the same as in the rats without splenectomy. The results of cpm values and SI ratio of PHA-induced blastogenesis, and NK-activity indicated that immunological competency of spleen cells of tumor bearers was reduced during the early tumor-bearing period and the late tumor bearing period, while it was increased in the middle tumor bearing period. Tumor growth following splenectomy was considered to be controlled by immunological competency of spleen cells. Thus, it may not be unreasonable that tumor growth is inhibited on some occasions and it is facilitated on other occasions after splenectomy.