Despite the high incidence of allergic transfusion reactions (ATRs), the mechanisms that underlie these reactions are not well described. The program presenters, will review the current data on the epidemiology, prevention and mechanisms of ATRs. The presenters, will also discuss the following; the role of plasma and the mitigation strategy of plasma removal, the role of donor versus recipient factors in the etiology of ATR, the characterization of leukocyte and platelet activation markers/signaling pathways that may be activated in patients with a history of ATRs. Strategies targeting these pathways to better prevent ATR will also be presented.