Granulocytes are innate immune cells that contain specialized granules to provide the first line of immune defense. Upon arrival at the site of infection, they participate in the inflammatory reaction by phagocytosis and intracellular killing of bacteria, the production of inflammatory mediators and the release of cytotoxic enzymes and proteins. 

There are three basic types of granulocytes: neutrophils, basophils, and eosinophils.

Neutrophils, which constitute 50-70% of the circulating white blood cells are much more numberous than eosinophils (1-3%) or basophils (<1%).

Types of Granulocytes

1: Neutrophils are the ost abundant WBC in blood. They leave the blood and enter tissues to phaogcytize foreign material. An increase in neutrophils in the blood is indicative of a systemic bacterial infection. Because of the variation in nuclear appearance, they are also called polymorphonuclear neutrophils (PMNs). Neutrophile granuloctyes contain myeloperoxidase-rich azurophil granules.

2. Eosinophils are also phagocytic and can migrate from the blood into the tissue spaces. Eosionphil granuloctyes contain the peroxidase, the eosinophil peroxide with sahres about 70% DNA homology with myeloperoxidase. 

3. Basophils secrete histamine to help mediate inflammatory reactions and are closely related in function to mast cells.

Identification of the different Granulocytes

The granulocytes are classified as neutrophils, eosinophils, or basophils on the basis of cellular morphology and cytoplasmic staining characteristics. The different pattern of peroxidase contained in the white blood cell fraction is the basis for leukocyte differentiation by an automatic blood cell counter, the Bayer/Technicon H3.

Goumenlouk (US6,046,019) discloses a method for detecting granulocytes where a blodo sample is dran, components that might interfere with the assay are remove/neutralized, the granulocytes present int he sample are disrupted to release intracellular myleoperoxidase and then the sample is contacted with a peroxide and a chromogenic donor dye. The MPO enzyme catalyzes hydrogen peroxide involved reactions which result in the dye changing color ir, and to the extent that, granulocytes are present in the blood sample.