Neutrophil
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More Specific Terms
Function
- steps in neutrophil function:
- response to chemotactic factors
- adhesion to vascular endothelium
- passage through tight junctions between endothelial cells
- adherence, phagocytosis & lysis of infectious agent
Pathology
- contents of neutrophil granules activated & released outside of phagocytic vacuoles can result in inflammation, tissue injury, & tissue necrosis
- disorders associated with neutrophil function:
- disorders resulting in neutropenia
- chemotherapy
- radiation therapy
- adverse drug reaction
- risk of infection increased markedly when the absolute neutrophil count drops below 500-1000/ uL (see neutropenia)
- abnormal neutrophil phagocytosis & bactericidal activity
- alcoholism & cirrhosis
- type-2 diabetes mellitus
- prolonged corticosteroid use*
- absence of antibodies or complement components required to opsonize micro-organisms
- disorders of neutrophil chemotaxis
- * most common cause of disordered neutrophil phagocytosis
Biochemistry
- neutrophils express chemokine receptor CXCR1 & CXCR2 responsible for the migration of neutrophils in response to chemokines
- neutrophils also have receptors for the Fc part of IgG ( Fc gamma receptor) & for complement C3
- surface markers:
Physiology
- for each neutrophil in peripheral blood, about 16 myeloid precursors are present in the bone marrow
- about 5 mitotic divisions from myeloblast to neutrophil, with 3 at the myelocyte stage takes about 14 days
- the last 6-7 days of development are spent in the maturation & storage pool
- neutrophils enter the peripheral blood & distribute between a circulating pool (measured in the leukocyte count (WBC count) & neutrophil count & a marginated pool along vessel walls or in capillary beds ( margination or pavementing of neutrophils)
- marginated neutrophils can be rapidly mobilized
- neutrophils enter tissues randomly in the absence of chemotactic signals & leave the body in a fw days via secretions from bronchi, saliva, GI tract, or urine, or are destroyed by the reticuloendothelial system [3]
- neutrophils move in a zigzag fashion, but in a straight line in response to neutrophil chemotactic factor(s)
- neutrophils are the 1st cells to arrive at sites of bacterial infections & fungal infections
- neutrophils are phagocytes, sequestering pathogens in phagocytic vacuoles
- degranulation of cytoplasmic granules into the vacuoles with activation & release of myleoperoxidase & other enzymes into the vacuoles provides bactericidal activity
Laboratory
- normal neutrophil count is 3000-6000/ uL, & 50-70% of circulating WBC
- assessment of neutrophil function
- chemotaxis
- bactericidal activity
- nitroblue tetrazolium dye reduction test for abnormalities in neutrophil oxidative metabolism
More General Terms
Additional Terms
- CD10 (neprilysin, neutral endopeptidase, enkephalinase, common acute lymphoblastic leukemia antigen, CALLA, atriopeptidase, MME, EPN)
- CD11b; integrin alpha-M; cell surface glycoprotein MAC-1 subunit alpha; CR-3 alpha chain; leukocyte adhesion receptor MO1; neutrophil adherence receptor; CD11 antigen-like family member B; (ITGAM, CD11B, CR3A)
- CD13 (aminopeptidase-N, aminopeptidase-M, gp150, microsomal aminopeptidase, ANPEP, PEPN)
- CD14; monocyte differentiation antigen CD14; myeloid cell-specific leucine-rich glycoprotein
- CD15, Lewis X or X-hapten
- CD16, Fc gamma receptor III or Fc gamma receptor (low affinity)
- CD33; myeloid cell surface antigen CD33; sialic acid-binding Ig-like lectin 3; siglec-3; gp67 (SIGLEC3)
- granulocyte transfusion
- neutropenia
- neutrophil count
- Pelger-Huet anomaly
- phagocytic disorder
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 352
- Henry's Clinical Diagnosis & Management by Laboratory Methods, 21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co., Philadelphia, PA. 2007, page 495
