Stimulation of human neutrophils with sera containing HLA Class I alloantibody causes preferential degranulation of azurophilic granules and secretory vesicles

Abstract

The activation of neutrophils by human leukocyte antigen (HLA) Class I alloantibody is thought to be involved in transfusion-related acute lung injury. Neutrophils contain various biological substances in four groups of granules, including secretory vesicles, azurophilic granules, specific granules and gelatinase granules. To characterize the activation of neutrophils by HLA Class I alloantibody, we investigated whether HLA Class I alloantibody could cause the degranulation of these groups of granules either coordinately or selectively. Sera containing HLA-A24 alloantibody were incubated with neutrophils in a washed whole blood system. CD11b expression (secretory vesicles) on neutrophils was analysed by flow cytometry, and the secretion of markers of each granule was determined by ELISA. The treatment of cross-matching-positive neutrophils with sera containing HLA-A24 alloantibody caused the significant expression of CD11b, and the significant secretion of neutrophil elastase and myeloperoxidase, azurophilic granule markers and heparin-binding protein (HBP), which is localized in secretory vesicles and azurophilic granules when compared with cross-matching-negative neutrophils. In contrast, no significant differences were observed in the secretion of lactoferrin, a marker of specific granules, and matrix methalloproteinase-9, a marker of gelatinase granules between cross-matching-positive and cross-matching-negative cells upon stimulation with sera. CD11b expression and secretion of HBP by serum was partially inhibited by p38 mitogen-activated protein (MAP)-kinase inhibitors. Neutrophils activated with sera containing HLA Class I alloantibody caused the preferential degranulation of azurophilic granules and secretory vesicles. This process was at least in part mediated by p38 MAP kinase-involved signal transduction.