Leukocyte elastase release during blood coagulation. A potential mechanism for activation of the alternative fibrinolytic pathway.

Immunological detection of elastase, an enzyme present within leukocyte granules, has been used as a marker for polymorphonuclear leukocyte activation. Polymorphonuclear leukocytes contained 4.6 mug/10(7) cells, whereas erythrocytes, mononuclear cells, and platelets contained <1% of this level. In plasma that was separated from blood cells after 1 h at 22 degrees C, the mean level of elastase-related antigen in seven normal donors was 25+/-6 ng/ml. This level was unaltered by immediate separation of the plasma from the cells, by inclusion of protease inhibitors, or by anticoagulation of the plasma with either EDTA or acidcitrate-dextrose (the level in heparinized plasma was approximately threefold higher). In serum, the level of elastase-related antigen was 288+/-125 ng/ml, representing an 11.5-fold increase above plasma levels. The antigen detected in serum was immunochemically indistinguishable from the leukocyte enzyme. Release of elastase was observed when isolated polymorphonuclear leukocytes were added to nonanticoagulated platelet-rich or platelet-poor plasma, recalcified plasma, or to serum. Addition of a chelating agent to serum prevented elastase release, but calcium or magnesium did not induce release in the absence of plasma. Coagulation induced by addition of thrombin to plasma also failed to induce release. In whole blood or in anticoagulated plasma reconstituted with polymorphonuclear leukocytes and then recalcified, initial release of elastase occurred concomitantly with or slightly after clotting and reached maximal levels within 20-40 min after clot formation. The data indicates that early events in coagulation or other pathways that occur in parallel with coagulation induce leukocyte release. The release of elastase, a major fibrinolytic protease of leukocytes, from the cells provides a mechanism for this enzyme or other granule proteases to participate in physiological events.