Tehran University Medical Journal

Blood transfusion is commonly implemented to manage life and health-threatening conditions on a rapid and short-term basis. Over the years, ongoing technical advances have dramatically improved transfusion medicine to provide more safety and effectiveness. However, transfusion is still complicated with different adverse events that mainly induced by the presence of allogeneic leukocytes in the blood products. Several lines of evidence have shown that leukocytes in blood components are involved in the induction of febrile nonhemolytic transfusion reactions (FNHTRs), HLA alloimmunization and platelet refractoriness as well as the increased risk of the infectious diseases transmitted by leukotropic viruses including cytomegalovirus (CMV), human T-lymphotropic virus (HTLV)-I/II and Epstein-Barr virus (EBV). During current decades, introducing various leuko-reduction techniques have shown to be associated with less transfusion related adverse events and improved clinical outcomes. The lower incidence and severity of febrile transfusion reactions; reduced risk of transfusion related transmission of CMV or other leukocyte-associated infections, lowered incidence of alloimmune platelet refractoriness in addition to reducing risk of mortality and morbidity in patients are considered as clinical benefits of leuko-reduced products. Currently, by the use of 3^rd and 4^th generation of filters, the highest levels of leukoreduction in blood components have been achieved. Filtration techniques have also the advantages of being performed shortly after preparation of components (pre-storage) or post-storage even at the patient’s bedside. However, it seems that pre-storage depletion of leukocytes provides better protection than post-storage techniques due to the elimination of leukocyte-derived cytokines effects which are increasingly released during storage. Particularly in platelet products, the earlier depletion of leukocyte also favors less platelet-induced leukocyte activation which may be triggered by the interaction between either activated platelets or their released chemokines and residual leukocytes during storage. Despite the benefits attributed to leukoreduction of blood components, the global use of leukoreduced products is commonly hampered by its high cost especially in developing countries in which leukoreduction of blood components is usually limited to some patients with special conditions. In this review, after briefly introducing of some transfusion adverse events that are attributed to allogeneic leukocytes existed in blood products, the effects of leukoreduction process in the attenuation of these events will be discussed.