Abstract

Homologous blood transfusion has been implicated as a modulator of the host immune system in a number of clinical settings. Improved renal allograft survival is observed in patients receiving pretransplant transfusions. Decreased recurrence of active inflammatory bowel disease has been recently reported in transfused patients with Crohn's disease. Conversely, deleterious immunomodulatory effects of transfusion may explain the association between transfusion and increased susceptibility to cancer recurrence and bacterial and viral infection. Clinical studies regarding cancer recurrence and transfusion are retrospective and conflicting. There is epidemiologic evidence for more rapid progression of HIV-1 infection in heavily transfused patients. Studies on transfused surgical patients have shown transfusion to be associated with an increased frequency of postoperative bacterial infections. Some studies have come to different conclusions. These investigators have suggested that transfusion may represent a surrogate marker for other risk factors for infection. Animal models designed to control for confounding factors have supported an association between transfusion and bacterial infection severity in most, but not all, reports. Attempts to define the immunologic alterations associated with transfusion have revealed a generalized impairment of cellular immunity in both humans and animals. Although the preponderance of data supports an association between perioperative transfusion and increased susceptibility to postoperative bacterial infection, it is not certain to what extent this relationship constitutes cause and effect.