[Experimental study on immunological effect of splenectomy on tumor-bearers]

In view of popularity of splenectomy in combination with gastrectomy for gastric cancer, immunological effect of splenectomy was studied experimentally, using SD rats and 3-methylcholanthrene-induced mammary cancer, MRMT -1. Splenectomy was performed on day -14, 2, 7, 14 or 21 of sc inoculation of 200 mg (about 4 X 10(6) cells) of MRMT -1 at the back of 4-week-old female rats. Tumor growth and immunocompetence of peripheral lymphocytes, spleen cells and thymus cells were examined. Tumor growth on day 35 tended to be inhibited in rats splenectomized on day -14, 2, or 14, while it tended to be promoted in rats splenectomized on day 7. PHA-induced blastogenesis and NK activity of spleen cells were reduced on day 2, rose on day 7 and gradually decreased on days 14 and 21. Winn's neutralization assay revealed that spleen cells on days 2, 14 and 21 of tumor inoculation had suppressor activities. In conclusion, spleen cells of tumor-bearing rats showed a reduced immunocompetence on day 2 (the early tumor-bearing stage) and on day 14 and later (the late tumor-bearing stage), while they showed a raised immunocompetence on day 7 (the middle tumor-bearing period).