Granulocyte eosinophile

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 30.01.2023

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

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

The development of eosinophil granulocytes in the bone marrow is regulated by activated T lymphocytes via the messenger substance interleukin-5.

Eosinophilic granulocytes occur in large numbers at sites of inflammation and in response to various infections with parasites. Cytoplasmic granules containing positively charged proteins characterize these cells. The granule proteins are strongly basic (pH > 10) and therefore bind strongly acidic dyes, specifically the red-orange dye eosin, after which the cells are named.

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

General information
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  • When activated eosinophilic leukocytes degranulate, 4 highly basic proteins enter the surrounding tissue:
  • Eosinophil cationic protein(ECP)
  • Eosinophil-derived neurotoxin(EDN)
  • Eosinophil peroxidase(EPO)
  • Major basic protein(MBP).

One of these proteins, ECP, is useful for monitoring many active inflammatory diseases because the level of circulating ECP often reflects the status of inflammation.

ECP has toxic effects on neurons, some epithelial cell lines, and isolated myocardial cells. Although circulating ECP levels vary widely among patients, some studies support the usefulness of ECP measurements as a marker of inflammation. ECP concentrations in plasma and other body fluids increase in inflammatory responses characterized by eosinophil activation. The neuronal toxicity of ECP can lead to pruritus, and circulating ECP levels may provide an indication of the severity of various skin diseases. There is evidence that serum ECP levels reflect the activity of atopic eczema (and also allergic bronchial asthma). This correlation is higher than that of total serum IgE levels with clinical symptoms. In principle, however, it should be noted that ECP determinations from serum are subject to considerable interindividual variation.

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In the skin, eosinophilic granulocytes are often found near peripheral nerve fibers in inflammatory allergic diseases. Thus, eosinophilic granulocytes are in direct contact with peripheral nerves in prurigo nodularis .

EDN and ECP have neurotoxic effects. EDN can be detected in lesions of patients with prurigo nodularis.

ECP is found more frequently in inflammatory skin in atopic eczema. It correlates here with the severity of the inflammatory reaction.

Eosinophilic granulocytes can release neurotrophins such as NGF (nerve growth factor) and BDNF (brain-derived-neurotrophic factor). BDNF prevents apoptosis of eosinophilic granulocytes.

Neurotrophins are known for their neurotrophic and neuroprotective activity. Furthermore, neurotrophins induce chemotaxis of eosinophilic granulocytes. Therefore, they represent important mediators for influencing cutaneous inflammation. They play an important role in the process of sensitization and in the development of pruritus.

Neurotrophins are the mediators that establish bidirectional interaction between nerve fibers and eosinophilic granulocytes. They induce myelination, differentiation and outgrowth of nerve fibers. This may also explain the hypertrophy of peripheral nerve fibers in atopic eczema and prurigo nodularis. Furthermore, they prevent the programmed cell death(apoptosis) of the nerve fibres. Neurotrophins can also modulate the functional activity of neurogenic cells. Besides neurotrophins, eosinophilic granulocytes can also release neuropeptides such as substance P, VIP (vasoactive intestinal peptide). Both mediators are involved in mediating pruritus.

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Last updated on: 30.01.2023