Diseases with Eosinophilia
Eosinophilic granulocytes are involved in immune processes in a complex way and involving very different functions. At sites of inflammation, they release toxic substances that kill intracellular pathogens. However, these toxic substances can also cause c
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Introduction
The eosinophilic granulocyte was described originally by Paul Ehrlich in 1879, and its name is based on the staining pattern of its cellular granules with eosin. Eosinophils are bone marrow-derived cells and normally make up 1–5% of the peripheral leukocytes of human blood. They are primarily tissue-resistant cells. The number of tissue cells to circulating cells is about 100:1. Eosinophilic granulocytes are involved in immune processes in a complex way and with very different functions. They are the most important effector cells of antibodydependent cell-mediated toxicity in worm infections. At sites of inflammation, they release toxic substances, such as major basic protein (MBP), eosinophilic cationic protein (ECP), lysophospholipase, peroxidases, and oxygen radicals, which kill intracellular pathogens. However, these toxic substances can also cause considerable tissue damage. Antibodies directed against major basic protein or eosinophilic cationic protein can be used to investigate the role of eosinophils and their activation status in skin and allergic diseases. Eosinophils also play an important role in allergic reactions, in which they act in close association with IgE antibodies and are increasingly found in tissues with immediatetype IgE-mediated immune responses. They express receptors for IgE antibodies, in particular the high-affinity receptor FcεRI, and can bind IgE-coated particles. If an allergen is injected intradermally, the migration of eosinophilic granulocytes into the skin can be observed after 24 h. In atopic eczema, it is suspected that the prolonged lifespan and presence of eosinophilic granulocytes are due to an apoptosis block. Since mature eosinophils no longer divide and spontaneously undergo apoptosis, factors that
J. C. Simon (*) Clinic and Polyclinic for Dermatology, Venerology and Allergology, University Hospital Leipzig, Leipzig, Germany e-mail: [email protected] © Springer-Verlag GmbH Germany, part of Springer Nature 2020 G. Plewig et al. (eds.), Braun-Falco´s Dermatology, https://doi.org/10.1007/978-3-662-58713-3_43-1
activate them and prolong their lifespan, such as interleukin-5, GMCSF, and interleukin-3, are crucial for the duration and severity of eosinophilic inflammation. Interleukin-5 in particular is the most important growth and maturation factor for eosinophilic granulocytes. In addition to their role as effector cells of the inflammatory response, eosinophilic granulocytes can also exert a direct immunomodulatory effect. They release a variety of proinflammatory mediators, cytokines, and growth factors, including interleukin-2, -4, -5, -10, -12, -13, -16, -18, TGF-α/β, lipid mediators, free oxygen radicals, and mitochondrial DNA. The interaction between eosinophils and T cells is also essential. Thus, as antigen-presenting cells (APC), they can be effective in stimulating T cells, inducing the proliferation of CD4 +-T cells and promoting the secretion of Th2 cytokines. Propagation and activation of eosinophils are in turn controlled by the s
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