[The Role of the Spleen in Immunosuppression and the Effects of Splenectomy on Prognosis in Gastric Cancer Patients]

To elucidate the role of the spleen on the immunosuppression in gastric cancer patients, mechanism of the induction of suppressor cells in the spleen was investigated. Studies of tissue distribution of T cells using monoclonal antibodies revealed that spleen contained much higher proportion of OKT8 reactive T cells as compared with those in regional lymphnodes without metastasis. Lymphocytes released from the spleen during perfusion were taken to be representative of recirculating lymphocytes. Suppressor precursor cells were found to exist predominantly in perfusate from the spleen, while spontaneously activated suppressor cells were in the residual lymphocytes in the spleen after perfusion. Culture supernatants from splenic adherent cells induced suppressor cell activities as well as sera from splenic venous blood. These results suggest that suppressor precursor cells which could be mobilized slowly was more comparable to splenic lymphocytes and might be matured by factors released from splenic adherent cells, partly moving into peripheral blood. Furthermore, the effect of splenectomy on the prognosis of gastric cancer patients was investigated in randomized controlled trial. The patients who underwent total gastrectomy and had main location of the tumor on lesser curvature region were divided into two groups at random; splenectomy (+) and splenectomy (-) groups. A suggestive prolongation of survival time was observed in splenectomy (+) group. Thus, spleen seem to contribute to the immunosuppression in gastric cancer patients and splenectomy may lead to better prognosis.