[Gelatinase granules of the neutrophil granulocytes]

The neutrophil contains numerous granules of various composition and structure. For decades, the neutrophil was believed to contain only two granule types, peroxisomes (peroxidase-positive granules) and neutralohydrolasosomes (peroxidase-negative granules). Later existence of the third type distinguished by the presence of gelatinase hydrolyzing collagen and gelatin. Gelatinase was found in the granules that are lighter as compared to neutralohydrolasosomes and represent a subpopulation of peroxidase-negative granules. In addition to gelatinase, these granules contain beta-2 microglobulin, cytochrome b558, as well as receptor and adhesion proteins. Upon stimulation by inflammatory mediators, the gelatinase granules are secreted faster than the neutralohydrolasosomes. Their exocytosis mediates delivery of new adhesion proteins to the plasma membrane, which is required for maintenance of permanent and fast cell adhesion to the endothelium. The released gelatinase allows the neutrophil to penetrate through the basement membrane of the endothelium.