ABSTRACT
The primary role of the phagocytic leukocytes in host defenses is the ingestion and killing of invading microorganisms. The oxygen derivatives produced express toxicity either directly or by generation of additional reactive species on interaction with metal catalysts, phagocyte-derived enzymes, halide ions, or various nitrogenous compounds. The foregoing description of polymorphonuclear leukocyte (PMN) oxygen metabolism has many parallels in monocytes, macrophages, and eosinophils. PMN-derived oxidants are capable of injuring a variety of eukaryotic cells including tumor cells, erythrocytes, platelets, endothelial cells, fibroblasts, spermatozoa, lymphocytes, and phagocytes themselves. The products of oxygen reduction and of the Myeloperoxidase-hydrogen peroxide-halide system represent potent oxidizing agents by which PMN exert tumoricidal and microbicidal activity. Oxidant-dependent inactivation of soluble proteins by PMN has been shown to include granule enzymes and nonenzymatic proteins released by PMN during stimulation.
