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Author: Anoma Ranaweera, Medical Writer, Auckland, New Zealand. DermNet New Zealand Editor in Chief: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. October 2019.
The IL-17 cytokine family consists of six cytokines (interleukins 17A to 17F) and five receptors (interleukins 17RA to 17RE). The interleukins 17A, 17F, and 17A/F heterodimer ligands share a common receptor subunit (interleukin-17RA) for signalling.
IL-17 is mainly produced by a subset of CD4 cells named Th-17 (T–helper 17) cells. It is mainly secreted by activated CD4+ and CD8+ T lymphocytes, while its receptor is found on many cell types.
IL-17 has been classified as a pro-inflammatory cytokine because it induces the expression of mediators of inflammation involved in the proliferation, maturation, and chemotaxis of neutrophils.
Overproduction of interleukins 17A, 17F, and 17A/F is associated with tissue damage and autoimmune diseases such as:
Skin diseases associated with interleukin-17
The IL-17 family of cytokines play a role in the management of pathogens.
The same cytokines have also been reported to have functions outside the skin, at least trials involving mice. IL-17E has a protective role in CNS inflammation and participates in protective responses against parasites in the intestine [7–9].
Infections protected by IL-17
Skin diseases in which interleukin-17 is involved or is thought to be involved are as follows.
Psoriasis is a chronic inflammatory skin condition characterised by epidermal hyperplasia.
The role of IL-17 is under investigation in various forms of dermatitis.
IL-17 signalling has been associated with the development of skin cancer during chemical carcinogenesis in mouse models.
Epithelial skin cancers
The proinflammatory properties of IL-17 are protective against infection. A good understanding of the different roles played by the IL-17 cytokines is necessary to design effective drugs relating to pathogenesis and mechanisms of inflammation.
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