Granulocyte eosinophile

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Synonym(s)

Eosinophiles; eosinophil granulocyte; eosinophil granulocytes; Eosinophilia; eosinophilic leucocyte; eosinophil leukocytes; Eosinophils

Definition
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Normal value: In a differential blood count, 1-4% of leukocytes are normally found as eosinophil granulocytes. In absolute terms this is 50 to 250 cells per ul of blood. An increase in eosinophilic granulocytes is called eosinophilia.

Activated T-lymphocytes regulate the development of eosinophilic granulocytes in the bone marrow via the messenger substance interleukin-5.

Eosinophilic granulocytes occur in large numbers in inflammatory foci and in response to various parasitic infections. Cytoplasmic granulae containing positively charged proteins characterize these cells. The granulaproteins are strongly basic (pH > 10) and therefore bind strongly acidic dyes, especially the red-orange dye eosin, after which the cells were named.

Classification
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Eosinophilia is found in the following skin diseases and therapies see below Eosinophilia, skin changes.

General information
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  • When activated eosinophilic leukocytes degranulate, 4 highly basic proteins enter the surrounding tissue:
  • Eosinophilic cationic protein(ECP)
  • Eosinophil-derived neurotoxin (EDN)
  • Eosinophilic peroxidase (EPO)
  • Major basic protein (MBP).
  • One of these proteins, ECP, is suitable for monitoring many active inflammatory diseases, as the level of circulating ECP levels often reflects the status of the inflammatory event.
  • ECP has toxic effects on neurons, some epithelial cell lines and isolated myocardial cells. Although circulating ECP levels vary widely in patients, some studies support the usefulness of ECP measurements as inflammation markers. ECP concentrations in plasma and other body fluids increase during inflammatory reactions characterized by eosinophile activation. The neuronal toxicity of ECP may cause itching, and circulating ECP levels may give an indication of the severity of various skin diseases. There is evidence that serum ECP levels reflect the activity of atopic eczema (and also of allergic bronchial asthma). This correlation is higher than that of total serum IgE levels with clinical symptoms. In general, however, it should be noted that serum ECP determinations are subject to considerable inter-individual variation.

Note(s)
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  • In the skin, eosinophil granulocytes are often found near peripheral nerve fibres in inflammatory allergic diseases. For example, eosinophilic granulocytes in Prurigo nodularis are in direct contact with peripheral nerves.
  • EDN and ECP have neurotoxic effects. EDN can be detected in lesions of patients with Prurigo nodularis.
  • ECP is increasingly found in inflammatory skin in atopic eczema. It correlates with the strength of the inflammatory reaction.
  • Eosinophil granulocytes can release neurotrophins such as NGF (nerve growth factor) and BDNF (brain-derived neurotrophic factor). BDNF prevents the apoptosis of eosinophilic granulocytes.
  • Neurotrophins are known for their neurotrophic and neuroprotective activity. Furthermore, neurotrophins induce chemotaxis of eosinophilic granulocytes. They are therefore important mediators for the influence of cutaneous inflammation. They play an important role in the process of sensitization and in the development of pruritus.
  • Neurotrophins are the mediators that create a bidirectional interaction between nerve fibres and eosinophilic granulocytes. They induce myelination, differentiation and growth of nerve fibres. This may also explain the hypertrophy of peripheral nerve fibres in atopic eczema and prurigo nodularis. They also prevent programmed cell death(apoptosis) of the nerve fibres. Neurotrophins can also modulate the functional activity of neurogenic cells. Besides neurotrophins, eosinophil granulocytes can also release neuropeptides such as substance P, VIP (vasoactive intestinal peptide). Both mediators are involved in the mediation of pruritus.

Literature
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  1. DOBES WL et al.(1947) Granulomatous Hodgkins' disease of the skin with extremeeosinophilia
    (eosinophilic granuloma of the skin?). Arch Derm Syphilol 55:212-221

  2. Jung Y et al (2014) Roles and regulation of gastrointestinal eosinophils in immunity and disease. J Immunol 193:999-1005
  3. Khoury P et al (2014) Eosinophils in vasculitis: characteristics androles
    in pathogenesis. Nat Rev Rheumatol 10:474-83

  4. Stand S (2008) Pruritus. UNI-MEd publishing house p. 41-42 Bremen

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Last updated on: 29.10.2020