['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, including human neutrophil elastase (HNE) also known as elastase-2 (ELA2), which may contaminate whole blood units and blood components.', 'The HNE concentration was determined in the supernatants of blood components with a commercial enzyme-linked immunosorbent assay (ELISA). The effect of leukocyte depletion and storage was evaluated by testing whole blood, buffy-coat-reduced, and leukocyte-depleted red cell units. Buffy-coat-derived platelets and plasma were also tested.', 'HNE concentrations at day 1 were about 50 microg/l in all types of red cell components with the exception of leukocyte-depleted red cells (<0.26 microg/l). In leukocyte-depleted red cells, platelets and plasma, no significant increase was observed during storage. In whole-blood units and buffy-coat-reduced red cells, the HNE concentrations increased steadily and often exceeded 1,000 microg/l when the units expired.'] Does leukocyte depletion of red cell components prevent exposure of transfusion recipients to neutrophil elastase?