Leukocyte depletion of red cell components prevents exposure of transfusion recipients to neutrophil elastase

Background: Polymorphonuclear leukocytes contain a large number of enzymes and bactericidal proteins stored in granules. Neutrophil activation induces degranulation and immediate release of these bioactive substances, includi ng human neutrophil elastase (HNE) also known as elastase-2 (ELA2), which m ay contaminate whole blood units and blood components. Materials and Method s: The HNE concentration was determined in the supernatants of blood compon ents with a commercial enzyme-linked immunosorbent assay (ELISA). The effec t of leukocyte depletion and storage was evaluated by testing whole blood, buffy-coat-reduced, and leukocyte-depleted red cell units. Buffy-coat deriv ed platelets and plasma were also tested. Results: HNE concentrations at da y 1 were about 50 mu g/l in all types of red cell components with the excep tion of leukocyte-depleted red cells (<0.26 mu g/l). In leukocyte-depleted red cells, platelets and plasma, no significant increase was observed durin g storage. In whole-blood units and buffy-coat-reduced red cells, the HNE c oncentrations increased steadily and often exceeded 1,000 mu g/l when the u nits expired. Conclusion: Leukocyte depletion may limit the inadvertent inf usion of bioactive substances derived from polymorphonuclear leukocytes, of which HNE is but one example. The accumulation of HNE in buffy-coat-reduce d red cells may be greater than that of whole blood units, HNE accumulates during storage and its quantity may have pathophysiologic significance. Pla telets and plasma derived from buffy coats contain some HNE, but leukocyte- depleted red cells virtually none. However, we consider the accumulation of HNE in these components not to be clinically important. The quantities, ki netics, and occurrence in various blood components of HNE contamination dif fer from those observed with cytokines. Copyright (C) 2000 S. Karger AG, Ba sel.