Specific degranulation of human polymorphonuclear leukocytes

Abstract

THE human polymorphonuclear leukocyte (PMN) contains two types of cytoplasmic granules, specific or heterophil granules and azurophil granules¹. These granules contain enzymes and various non-enzymatic proteins. The specific granule contains alkaline phosphatase and most of the lysozyme of the cell while the azurophil granule contains the acid hydrolases and other enzymes which identify it as a lysosome¹. Recent work² has shown that in the degranulation accompanying phagocytosis the specific or heterophil granules combine with the phagosome first, followed by the azurophil granules. This implies that degranulation may be a complex event with more than one signal involved. If this were true then one might expect that the events should be separable, that is, that one type of granule might be stimulated and the other little affected. Experiments in our laboratories have indicated that only one type of PMN granule responds to phorbol myristate acetate (PMA). Five minutes after application of nanogramme quantities of the agent the cell begins to show large intracellular vacuoles. Granules which demonstrate an alkaline phosphatase reaction disappear in 30 min while those staining for myeloperoxidase remain³. Here we report that PMA causes both a dose and a time dependent release of enzyme activity associated with specific granules while those associated with azurophil granules or lysosomes remain associated with the cell as did a cytoplasmic marker enzyme glucose-6-phosphate dehydro-genase.