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Neutrophils (Neutrophilia, Neutropenia)



DEFINITION


Blood leukocyte with segmented nucleus and inconspicuous cytoplasmic granules. Its primary functions during inflammation are phagocytosis and killing bacteria.



SYNONYMS


Polymorphonuclear neutrophil (PMN), segmented neutrophil



TYPICAL NORMAL RANGE


Dogs: 3-11.5 × 103 neutrophils/μL. Cats: 2.5-12.5 × 103 neutrophils/μL.



PHYSIOLOGY


Precursors in bone marrow respond to colony-stimulating factors produced during inflammatory and immune responses. Mature neutrophils are initially retained in marrow as part of storage pool. In blood, neutrophils occur either in the circulating pool or are associated with endothelial cells as marginal pool and then migrate into tissue. Neutrophils circulate for only a few hours. In blood samples collected for CBC, only neutrophils in the circulating pool are counted.



CLINICAL APPLICATIONS


CAUSES OF ABNORMALLY HIGH LEVELS (NEUTROPHILIA)


• Inflammation, whether acute or chronic, infectious or noninfectious. If acute inflammation, left shift and/or toxic changes may be present.

• Stress leukogram (glucocorticoids shift neutrophils from marrow storage pool and from marginal pool into circulating pool).

• Excitement leukocytosis (increased blood flow shifts neutrophils from marginal to circulating pool).

• Paraneoplastic production of colony-stimulating factor

• Granulocytic leukemia

• Canine leukocyte adhesion deficiency

NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Assess for cause depending on clinical signs.


CAUSES OF ABNORMALLY LOW LEVELS (NEUTROPENIA)


• Intense inflammation, especially if bacterial cause (increased tissue demand)

• Endotoxemia (shift from circulating to marginal pool)

• Acute parvoviral infection (decreased marrow production and endotoxemia)

• Decreased granulopoiesis (e.g., feline leukemia virus [FeLV] infection, feline immunodeficiency virus [FIV] infection, drugs [see below], myelophthisis)

• Destruction of mature neutrophils (e.g., immune-mediated neutropenia)

• Previous use of recombinant human colony-stimulating factor
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on N

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