Neutrophilia

Neutrophils are derived from same precursor as monocytes. Cytoplasm contains granules; the nucleus has 3-4 segments. Functions include chemotaxis—neutrophils migrate to sites of inflammation by chemotactic factors e.g. complement components (C5a and C3), and cytokines. Cytotoxic activity is via phagocytosis and destruction of particles/invading microorganisms (latter often antibody coated = opsonised). Granules 134 contain cationic proteins—>lyse Gram -ve bacteria, 'defensins', myeloperoxidase—interacts with H2O2 and HCl—►hypochlorous acid (HOCl); lysozyme (hydrolyses bacterial cell walls); superoxide (O2-) and hydroxyl (OH-) radicals. Neutrophil lifespan is ~1-2d in tissues.

Normal neutrophil count 2.0-7.5 x 109/L (neonate differs from adult; see Normal ranges p690).

Neutrophilia is defined as an absolute neutrophil count >7.5 x 109/L.

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