An azurophilic granule is a cellular object readily stainable with a Romanowsky stain.
In white blood cells and hyperchromatin, staining imparts a burgundy or merlot coloration.
Neutrophils in particular are known for containing azurophils loaded with a wide variety of anti-microbial defensins that fuse with phagocytic vacuoles.
Azurophils may contain myeloperoxidase, phospholipase A2, acid hydrolases, elastase, defensins, neutral serine proteases, bactericidal permeability-increasing protein,[1] lysozyme, cathepsin G, proteinase 3, and proteoglycans.
These cells are similar in size to so-called heterophils with abundant cytoplasm that is finely to coarsely granular and may sometimes contain vacuoles.