Enhancement of Immunologically Induced Granule Exocytosis from Neutrophils by Cytochalasin B

Abstract

Polymorphonuclear neutrophil leukocytes (neutrophils) release granule enzymes to the extracellular medium after adherence to immune complexes or aggregates attached to surfaces too large to be phagocytosed (1–4). A number of facts have emerged in the past few years that define this phenomenon. The release has been shown to occur by direct exocytosis of granules along the neutrophil membrane in contact with the surface but not along the free, unattached membrane of the cell (2, 5). It requires stimulation by aggregated immunoglobulin G immune complexes, or complement on the surface, but not aggregated IgM, IgD, IgE or proteins unrelated to immunoglobulins (6). The release of granular enzymes requires calcium in the external medium and glycolytic metabolism on the part of the neutrophil. It is accompanied by stimulation of glucose oxidation by the hexose monophosphate pathway, but this is not required for the secretion. The release can be inhibited by diisopropyl fluorophosphate and agents which increase intracellular cyclic AMP (7, 8).