The killing of microbes and the destruction of ingested materials are accomplished by reactive oxygen species (ROS, also called reactive oxygen intermediates), reactive nitrogen species, mainly derived from nitric oxide (NO), and lysosomal enzymes. Neutrophils and monocytes contain granules packed with enzymes and anti-microbial proteins that degrade microbes and dead tissues and may contribute to tissue damage. These granules are actively secretory and thus distinct from classical lysosomes. Neutrophils have two main types of granules: The smaller specific (or secondary) granules contain lysozyme, collagenase, gelatinase, lactoferrin, plasminogen activator, histaminase, and alkaline phosphatase. The larger azurophil (or primary) granules contain MPO, bactericidal factors (such as defensins), acid hydrolases, and a variety of neutral proteases (elastase, cathepsin G, nonspecific collagenases, proteinase 3). Kumar V, Abbas AK, Aster JC. Robbins basic pathology. Elsevier Health Sciences; 2017. Page 68
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