In a normal, healthy person, neutrophils are found almost exclusively in the blood and bone marrow. In the blood, some neutrophils flow in the central axial stream with erythrocytes, platelets, and other leukocytes. These neutrophils are described as being in the circulating pool. Other neutrophils are found rolling along the vascular endothe-lium. These neutrophils are described as being in the marginal pool. Neutrophils in the circulating pool are in a dynamic equilibrium with neutrophils in the marginal pool.

An intrinsic property of neutrophils is to adhere to foreign surfaces and at sites of inflammation. At an inflammation site, neutrophils stick to the endothelium (adherence); migrate from the circulation, squeezing out between vascular endothelial cells (diapedesis) and ingest and kill micro-organisms. Adherence is mediated by integrins and selectins on the neutrophils and their receptors on the endothelium. Migration is mediated by chemotactic factors from the tissues interacting with chemotactic receptors of the neutrophils.

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