Effect of blood transfusions on macrophage-lymphocyte interaction in an animal model.

Blood transfusions have been reported over the last 2 decades to decrease allograft rejection, to increase the rate of tumor growth, and to increase susceptibility to infectious complications. The effect of transfusions on macrophages, specifically on their regulation of lymphocyte proliferation, was investigated. Both macrophages and their supernatants obtained from transfused rats impaired lymphocyte blastogenesis to a greater degree than those from nontransfused rats. This effect was greatest when the lymphocytes were subjected to mitogen stimulation. The immunosuppression was seen with macrophages from both allogeneically and syngeneically transfused rats. Blood transfusions exert their immunosuppressive effect at least in part by increasing macrophage suppression of lymphocyte response to stimuli.