These studies indicate that homologous blood transfusion affects the outcome of clinical diseases in both beneficial and adverse ways. Experimental situations are not suitable for randomized clinical trials - transfusions cannot be given to prevent the onset of diabetes or wound strength measured in man following receipt of homologous or autologous blood. These experimental observations indicate that the outcomes of numerous clinical diseases which have not been studied may be manipulated by the use of homologous blood or that transfusion should be avoided. Several studies indicate that changes in immune function following transfusion are permanent. The number of clinical phenomena associated with immune suppression and attributable to blood transfusion is unknown. SUMMARY Given the evidence presented here it would be foolish to suggest that transfusion of homologous blood has no immunologic consequences for the recipient. Blood transfusion is the oldest form of transplant - no one would argue that transplantation between unrelated individuals has no influience on the immune system. In organ transplantation the immunologic sequelae are permanent and there is evidence that the same is true following homologous blood transfusion. Lymphocytopenia is present one year following surgery for Crohn's disease if patients receive perioperative blood transfusion (43). Colorectal cancer patients transfused more than seven years prior to diagnosis have significantly reduced numbers of lymphocytes and lower natural killer cytotoxicity than colorectal cancer patients who have never been transfused (44). Transfusion of neonates causes suppression of lymphocyte reactivity which is still demonstrable 25 to 30 years later (45). There is evidence that transfusion at any time prior to elective surgery increases susceptibility to infectious complications (14) and otherwise healthy transfused individuals may be at increased risk of developing malignancies (46). All the longterm consequences of blood transfusion are not negative: Survival of transplants is prolonged by pretransplant transfusion and some women suffering from recurrent spontaneous abortion can deliver at term if previously transfused with their spouse's leukocytes. In the future we will be able to transfuse blood without causing immune perterbations and the consequent clinical phenomena. Studies presented here suggest that removal of donor leukocytes reduces the risk of infection and cancer recurrence. The technology has not reached the point of reducing the leukocyte number in transfused blood below 10^/unit. An alternative which is increasingly being utilized is autologous blood programs. Physicians are discovering that patients tolerate hemoglobin levels which were previously unacceptably low and many patients prefer being anemic over the risks of receiving homologous blood. Since transfusion is an identifier of high cost hospitalized patients, alternatives to routine blood use are being studied in hopes of safely reducing the costs of transfusion. REFERENCES 1. Jubert AV, Lee ET, Hersh EM, McBride CM. J Surg Res 15:399-403, 1973. 2. M 19 u4n ( s3t ) e3r4A6-M 35 , 2 W , i1n9c8h1u . rch RA, Keane RM, Shatney CH, Ernst CB, Nuidema GD. Ann Surg