Effects of human neutrophil elastase and cathepsin G on the reactivity of platelets with antiplatelet antibodies.

Two human neutrophil serine proteases, elastase (HNE) and cathepsin G (CathG), are known to change the structure and hemostatic function of platelet surface membrane. The platelet membrane contains glycoproteins (GPs) which function as alloantigens, autoantigens and targets of drug-induced antibodies. The aim of this study was to investigate whether proteolysis of platelet GPs by HNE and CathG is associated with changes in the reactivity of platelets to antiplatelet antibodies. The platelet immunoreactivity was examined using the MAIPA (monoclonal antibody-specific immobilization of platelet antigens) assay and PSIFT (platelet suspension immunofluorescence test). The treatment of platelets with HNE led to a moderate increase in their reactivity to quinidine-dependent (anti-GP Ib) antibody and to a slight decline in the expression of HPA-1a. In contrast, CathG did not provoke any significant changes in platelet reactions with quinidine dependent and anti-HPA-1a antibodies. Both enzymes had no significant effect on the expression of HLA-A2, HLA-A3, HLA-B7 and HLA-B8 on platelets.