Inactivation of heparin cofactor II by polymorphonuclear leukocytes

Inactivation of purified human heparin cofactor II by polymorphonuclear leukocytes was investigated. A proteolytic mechanism of inactivation was demonstrated by SDS-polyacrylamide gel electrophoresis. Inactivation and related proteolysis did not occur in the presence of unstimulated leukocytes and were prevented by various protease inhibitors. Heparin cofactor II was inactivated more rapidly than antithrombin III. However, heparin (1-10 ug/ml) strongly accelerated the rate of antithrombin III inactivation and slightly protected heparin cofactor II, thus reversing the order of inactivation. Dermatan sulfate had no effect on this process.