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eosinophil
Function:
- eosinophils are involved in allergic responses & are the 1st line of defense against helminths
- eosinophils are phagocytes
- phagocytosis of foreign particles
- phagocytosis of antigen-antibody complexes
- eosinophic granules contain inflammatory mediators
a) larger granules
1] major basic protein
2] acid hydrolases
3] eosinophil peroxidase
4] phospholipase
5] eosinophil cationic protein (ribonuclease-3)
6] eosinophil-derived neurotoxin (ribonuclease-2)
7] eosinophil protein X
b) smaller granules
1] arylsulfatase
2] acid phosphatase
- eosinophils also produce:
a) reactive oxygen species
b) LTC4
c) platelet-activating factor
d) cytokines
- eosinophils dampen inflammatory responses [3]
Physiology:
- derived from common granulocyte-monocyte stem cell in bone marrow -> committed eosinophilic progenitor cell
- 3 growth factors produced by lymphocytes affect eosinophil maturation (GM-CSF, IL2 & IL5)
- IL5 promotes terminal maturation & functional activation & prevents apoptosis of eosinophils
- 1/2 life in peripheral blood is ~ 18 hours after which they migrate into tissues where they survive for at least 6 days
- adrenocortical steroids expedite eosinophil migration from blood into tissues
- neutrophils in tissues are ~100 X more abundant than in blood
- within tissues they are found at epithelial barriers to the outside word, i.e. lung & respiratory tract, GI tract, skin
- eosinophil chemotactic factors:
a) leukotrienes
b) platelet-activating factor (PAF)
c) cytokines:
1] interleukin-5 (IL-5)
2] monocyte chemotactic protein
3] RANTES
- other factors in eosinophil recruitment
a) induction of VCAM-1 by endothelial cells b ) VCAM-1 binding of VLA-4 on eosinophils
Biochemistry:
- eosinophils express the chemokine receptor CCR3
Pathology:
- Charcot-Leyden crystals (a product of eosinophil degeneration) may be seen in areas of eosinophil accumulation
- inflammatory mediators of eosinophils are toxic to respiratory epithelial cells & result in shedding of these cells
- Creola bodies are clumps of sloughed respiratory epithelium in sputum of asthmatic patients
Laboratory:
- component of complete blood count with differential
- normal eosinophil count is 150-300/uL, & 1-4% of circulating WBC
- see ARUP consult [4]
Related
eosinophil peroxidase (EPX, EPER, EPO, EPP)
eosinophilia
eosinophilia-myalgia syndrome (EMS)
eosinophilic esophagitis
eosinophilic fasciitis (Shulman's syndrome)
eosinophilic folliculitis
eosinophilic gastroenteritis
eosinophilic granuloma
eosinophilic leukemia
eosinophilic pneumonia; Andrews syndrome; pulmonary eosinophilia
eosinophils in blood
eosinophils in urine
eosinophiluria
General
granulocyte
References
- Internal Medicine, Stein et al (eds), Little Brow & Co, Boston
1983, pg 1137
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998
- Henry's Clinical Diagnosis & Management by Laboratory Methods,
21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co.,
Philadelphia, PA. 2007, page 495
- ARUP Consult: Eosinophilic Diseases
deprecated reference
- ARUP Consult: Eosinophil-Related Disorders Testing Algorithm
https://arupconsult.com/algorithm/eosinophil-related-disorders-testing-algorithm