The effect of a single whole-blood transfusion on the cascade of cytokine secretion was studied in patients with chronic renal failure. The results indicate that 1 week after blood transfusion, no significant changes were observed in the secretion of interleukin-2, colony-stimulating factor, tumor necrosis factor, and gamma-interferon. However, 2 weeks after blood transfusion, a sharp decrease was observed in the generation of these cytokines. A decrease of about 70% was observed in interleukin-2, tumor necrosis factor, and gamma-interferon secretion. The production of colony-stimulating factor 2 weeks after blood transfusion amounted to about 30% less than baseline levels. No statistical differences in interleukin-1 production were observed throughout the study. In addition, we found that the decrease in cytokine secretion was paralleled by a sharp increase in the in vitro secretion of prostaglandin E2. Thus the beneficial effect of blood transfusion on graft survival might be due in part to an immunosuppressive effect brought about by immunoregulatory changes via the cascade of cytokine secretion.