Neutrophils, or polymorphoonuclear cells (PMNs), or heterophils are the commonest granulocytes and leukocytes, and are packed with granules that stain neutral (pink with H&E).

Neutrophils are phagocytic cells that normally circulate in the bloodstream. However, 'polys' quickly migrate into sites of infection or acute inflammation → after chemotaxis to reach the active sites, PMNs marginate along the vessel's endothelium, experience selectin-dependent capture and integrin-dependent adhesion, then extravasate into tissues, where they persist for 1-2 days. Neutrophils spend all their energy reserves in a self-and-pathogen-destructive respiratory burst, utilizing a NADPH oxidase complex that is assembled upon neutrophil activation.

Neutrophils contain specific, azurophilic, and tertiary granules:
specific granules
_ ● α-defensins – small cysteine rich, cationic proteins found in both invertebrates and vertebrates
_alkaline phosphatase
_ ● becteriocidal lactoferrin
_NADPH oxidase
azurophilic granules
_bactericidal/permeability increasing protein (BPI)
_serine proteasesneutrophil elastase and cathepsin G
tertiary granules
_cathepsin proteases

● neutrophils can also extrude neutrophil extracellular traps (NETs), a web of chromatin and serine protease fibers that trap and kill microbes extracellularly and independent of phagocytic activity

azurophilic granules are primarily lysozymes that are found in all three types of granulocyte

Tables  Complement Receptors  Cytokines  Fc receptors  Immune Cytokines  Immunoglobulins  Interferons  Scavenger Receptors  Toll-like Receptors


Labels: , , , , ,

. . . since 10/06/06