Recipient antigen-processing pathways of allogeneic platelet antigens: essential mediators of immunity.

Clinical studies have convincingly demonstrated that WBC reduction of blood components can reduce the incidence of primary HLA antigen alloimmunization at least in patients with acute myeloid leukemia.1 However, despite receiving WBC‐reduced platelets, approximately 19 percent of acute myeloid leukemia patients still became alloimmunized.1 In addition, it is not known whether WBC reduction will prevent HLA antigen alloimmunization among those recipients who have an intact immune system (e.g., general surgery patients). The biologic mechanisms responsible for immune stimulation by blood components are still incompletely understood but are probably related to both donor and recipient factors. Animal models have proven indispensable for elucidating the basic mechanisms of immunity against foreign antigens and several such models have been developed to study various aspects of transfusion immunobiology.2-4 Our laboratory has developed a murine transfusion model that has allowed us to focus on recipient factors affecting the immune response to WBC‐reduced platelets. This article will describe how the murine immune response to platelet transfusion is critically dependent on recipient antigen‐processing and‐presentation pathways and how these pathways can be exploited to modulate immunization against WBC‐reduced platelets.