MECHANISMS OF ALLOIMMUNIZATION AND IMMUNOSUPPRESSION BY BLOOD-TRANSFUSIONS IN AN INBRED RODENT MODEL

During refrigerated storage leukocytes in donor blood progressively un dergo apoptosis followed by secondary necrosis. Using an inbred rodent transfusion model, recipient animals received viable, necrotic, or ap optotic cells. While transfusion of viable blood MNCs stimulated produ ction of IgM, IgG(1) (Th2 type) and IgG(2a) (Th1-type) antidonor antib odies, leading to a suppression of subsequent DTH to donor antigens, t ransfusion of apoptotic donor cells led to neither alloimmunization no r immunosuppression. On the other hand transfusion of lysed donor cell s resulted in production of IgM and IgG(1) (Th2-type) antidonor antibo dies and to a strong suppression of subsequent DTH to donor antigens, Intravenously administered spleen cells that had been depleted of prof essional APCs and enriched for B cells stimulated IgM antidonor antibo dies but not IgG antibodies. Transfusion of such cells also led to sup pression of subsequent DTH to donor antigens, probably through inducti on of anergy or apoptosis in alloantigen-reactive recipient cells. Dep ending on the duration of blood storage any or all of these 4 classes of cells may be present and Th2 and/or Th1 effector mechanisms can be generated following blood transfusion.