Eosinophil granulocyte
From Wikipedia, the free encyclopedia
Eosinophil granulocytes, commonly referred to as eosinophils (or less commonly as acidophils), are white blood cells that are responsible for combating infection by parasites in the body. They also have a rather diverse array of other functions, impacting multiple areas of immunology including allergy and asthma.
Transparent in vivo, these cells appear brick-red when stained with eosin using the Romanowsky method (and are thus, 'eosin (or acid)-loving' cells, hence the name). Paul Ehrlich is considered the founder of the eosin-staining method. The red color is visible as small granules within the cellular cytoplasm. These granules contain histaminase and proteins such as eosinophil peroxidase, RNase, DNases, lipase, plasminogen, and Major Basic Protein that are toxic to both parasites and the host's tissues. Major Basic Protein comprises the hallmark crystalline core found in eosinophil secondary granules, which is released upon degranulation.
Eosinophils persist in the circulation for 6-12 hours, and can survive in tissue for an additional 2-3 days in the absence of stimulation.
Eosinophils make up about 1-5% of the all white blood cells, and are about 10-12 micrometers in size.
Eosinophils are found naturally in the thymus (cortico-medullary junction and medulla), lower gastrointestinal track, ovary during phases of the cycle, uterus, spleen, and lymph nodes. They are not found naturally in the lung, skin, or other organs. The presence of eosinohils in the lung, skin, esophogus, or internal organs is associated with a disease process.
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[edit] Eosinophil Development, Migration and Activation
- Eosinophil development in the bone marrow depends on IL-3, IL-5, and GM-CSF.
- Eosinophils have produced and stored most secondary granule proteins prior to exit from the bone marrow.
- A key mediator in eosinophil activation is interleukin 5.
- Eosinophils migrate to tissues in response to chemokines, such as eotaxin and RANTES, and leukotrienes, such as leukotriene B4 (LTB4).
- Eosinophils have effector molecules and functions at sites of activation:
-Cationic granule proteins
-reactive oxygen species
-lipid mediators (HETE, leukotrienes (LTB4 and the cysteinyl leukotrienes (LTC4, LTD4, LTE4), prostaglandin)
-enzymes (elastase)
-growth factors (TGF beta,VEGF,PDGF)
-cytokines (IL-1, -2, -4, -5, -6, -8, -13, TNF alpha)
-Antigen presentation (controversial)
[edit] Functions of eosinophils
- Eosinophils play a role in fighting viral infections which is evident from the abundance of RNAses they contain within their granules.
- Eosinophils also play a role in the allergic response, and in fibrin removal in inflammation.
- Eosinophils are considered the main effector cells in asthma pathogenesis and are associated with disease severity.
- Eosinophils fight helminth (worm) colonization and may be slightly elevated in the presence of certain parasites.
[edit] Eosinophilia
An increase in eosinophils, i.e. the presence of more than 500 eosinophils/microlitre of blood is called an eosinophilia, and is typically seen in people with a parasitic infestation of the intestines, a collagen vascular disease (such as rheumatoid arthritis), malignant diseases such as Hodgkin's Disease, extensive skin diseases (such as exfoliative dermatitis), Addison's Disease, and with the use of certain drugs such as penicillin. In 1989, contaminated L-tryptophan supplements caused a deadly form of eosinophilia known as eosinophilia-myalgia syndrome.
[edit] Eosinopenia
Eosinopenia is a decrease in eosinophil number, which occurs characteristically when glucocorticoids are administered or when the Cushing's disease is present. Dr. Harvey Cushing, the man who discovered the disease, identified Eosinopenia as one of the primary indicators in a patient suffering that disease. Over the years, with the increase in gluccorticoid therapy and the growing stresses in our society (another cause of a suppresed count), Eosinopenia has lost favor as a Cushing's diagnostic tool. That fact causes many people suffering Cushing's to often go undiagnosed for years until symptomatology is significant.
[edit] Treatment
Treatments used to combat eosinophils include:
- monoclonal antibody therapy against IL-5 - promote apoptosis
- antagonists of leukotriene synthesis or receptors
- corticosteroids- promote apoptosis
- Gleevec (STI571)- inhibits PDGF-BB in hypereosinophilic leukemia
[edit] Additional images
 Blood cell lineage |
[edit] External links
- Dorlands/Elsevier e_11/12336073
- Dictionary at eMedicine eosinophilic+leukocyte
- Bioweb at UWLAX Eosinophil
- Histology at ucsf.edu
[edit] References
Clin Exp Allergy. 2005 Aug;35(8):986-94
Science. 2004 Sep 17;305(5691):1773-6.
Curr Gastroenterol Rep. 2006 Oct;8(5):390-5. Review
Annu Rev Immunol. 2006;24:147-74. Review.
