neutrophil or polymorphonuclear leukocyte (PMN, poly)

^[1]^[2]^[3]^[4]^[5]

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

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

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:
- CD10, CD11b, CD13, CD14, CD15, CD16, CD33

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 few days via secretions from bronchi, saliva, GI tract, or urine, or are destroyed by the reticuloendothelial system^[3]
- 1/2 life of neutrophils in peripheral blood is ~ 5 days^[5]
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

↑ 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
↑ ^3.0 ^3.1 Henry's Clinical Diagnosis & Management by Laboratory Methods, 21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co., Philadelphia, PA. 2007, page 495
↑ ^4.0 ^4.1 ARUP Consult: Neutrophil Disorders deprecated reference
↑ ^5.0 ^5.1 Pillay J Response: The in vivo half-life of human neutrophils. Blood. 2011 117(22) http://www.bloodjournal.org/content/117/22/6053?sso-checked=true