The neutrophil. Function, disorders, and testing.

Normal neutrophil function requires the cooperation and coordination of many cellular activities within the neutrophil and cells of the vascular system. The free flowing neutrophil begins the process by "rolling" along the vessel wall. This first step in migration is mediated by selectins on the surface of neutrophils, platelets, and endothelial cells. Subsequent firm adhesion requires the collaboration of neutrophil integrins and membrane-expressed cellular adhesion molecules. The activated neutrophil also changes shape from a sphere to an elongated motile cell by the assembly of actin filaments. At the inflammatory focus the neutrophil may encounter material to be ingested and killed. The ingestion process is mediated by the same receptors that stimulate firm adherence to the vessel wall. The ingestion process stimulates the formation of active NADPH oxidase, which is critical for the formation of superoxide and subsequent components of the killing mechanism. The process of normal neutrophil function is complex and multifaceted, but luckily, defects in this system are extremely rare. Patients with persistent and recurrent infections should be carefully evaluated for underlying disease before primary neutrophil dysfunction is pursued.