The Cellular Players

The neutrophil granulocyte

Neutrophils are short-lived, bone marrow-derived (half-life 6 hours), circulating white blood cells with a diameter of about 5.5 µM. on ultrastructure (see fig: 1.20) they contain a large number of cytoplasmic granules, which in turn contain a large number of powerful agents (see table 1.2), many of which when secreted can aid the cell’s rapid transit through tissues, and prompt phagocytosis and destruction of bacteria. Neutrophils are the archetypal acute inflammatory cells they are highly responsive to chemotactic mediators, e.g. IL-8 and C5a, and are the first cells to emigrate to the inflamed site (see below). The importance of the neutrophils in host defense is emphasized by the greatly increased susceptibility to infection found in patients with neutropenia or inherited disorders of neutrophil function. A number of diseases have been linked with rare inherited abnormalities in neutrophil granules. Most of these are characterized by repeated bacterial infections. Chronic granulomatous disease due to a defect in NADPH oxidase is perhaps the best-recognized example.

 

Table 1.2 Constituents of human neutrophil granules
	Azurophil granules	Specific granules
Microbicidal enzymes	Lysozyme Myeloperoxidase	Lysozyme
Neutral proteinases	Elastase Collagenases Cathepsin G	Collagenase
Acid hydrolases	Phosphatases Lipases Sulphatases Histonase Cathepsin D B glycerophosphatase Esterase Neuraminidase 5’ nucleotidase	Phosphatases
Others	Bactericidal/ Permeability-inducing protein Defensins Cationic proteins Glycosaminoglycans Chondroitin sulphate Heparin sulphate	Lactoferrin Vitamin B12 binding protein C3bi receptor Cytochrome B Flavoproteins