Effects of splenectomy on pulmonary metastasis and growth of SC42 carcinoma transplanted into mouse liver

The carcinoma SC42 was transplanted into the liver of its syngeneic mice DS, and the immunological integrity of the spleen and the effects of splenectomy on the growth and pulmonary metastasis of the liver tumor were assessed. On day 7 after liver tumor transplantation, the natural killer (NK) activity of the splenocytes was significantly elevated; it subsequently decreased at a later stage of the tumor. The response of the splenocytes to PHA and Con‐A decreased significantly from the early stage of the tumor. However, the mixed lymphocyte‐tumor cell reaction increased significantly from day 14 to day 28. The survival rate of the mice, which had undergone simultaneous splenectomy and liver tumor transplantation, was significantly lower than that of sham‐operated control mice. The number of pulmonary metastases in splenectomized mice was significantly greater than in the control mice. There was, however, no difference between the two groups in the weight of the liver tumor. By contrast, splenectomies performed 14 days before or 14 days after tumor transplantation had no significant influence on the survival of the mice. Splenectomies performed on day 0 and on day 3 after tumor transplantation significantly increased the number of pulmonary metastases, Furthermore, the intravenous injection of anti‐asialo GM1 antisera on day 0 and day 3 significantly increased the number of pulmonary metastases, but injection of anti‐Thy 1,2 antisera had no effect. These results suggest that splenic NK cells may play an important role in the suppression of pulmonary metastasis at early stages of the liver tumor.