The effect of immunosuppressive therapy on the phagocytic and metabolic functions of the reticuloendothelial system in renal transplant recipients.

The object of this study was to examine the bearing that immunosuppressive therapy may have on the phagocytic and metabolic functions of the reticuloendothelial system (RES). The phagocytic and metabolic activities of the RES were determined in renal graft recipients before transplantation and at intervals afterwards. The activities were measured as the plasma clearance rate of 125I-labelled microaggregated human serum albumin and the increase in the plasma metabolites of this test substance. The intravascular clearance of microaggregated albumin was significantly depressed at 1-12 days (P less than 0.001), 1.4 months (P less than 0.02) and 6-9 months (P less than 0.01) after transplantation compared to the levels before operation. RES phagocytosis was normal in the 1-3 year group. Furthermore, in all except the 1-4 month group the metabolic activity was significantly reduced. The significant impairment of the RES functions immediately after transplantation was probably due to administration of antilymphocyte globulin and extremely high doses of steroids. After antilymphocyte globulin had been withdrawn the phagocytic capacity of the RES was correlated to the total dose of steroids given over the 12 months prior to the test. The azathioprine regime seems to have had no influence on the RES functions.