title: A systematic review of the role of interleukin-17 and the interleukin-20 family in inflammatory allergic skin diseases.
abstract: Allergic skin diseases include atopic dermatitis/eczema, contact dermatitis, and drug hypersensitivity. Allergic skin diseases have a high prevalence. Atopic dermatitis is one of the most common inflammatory skin diseases and similar for allergic rhinitis and allergic asthma. Over a long period, allergic diseases have been regarded as immunoglobulin E-mediated T-helper-2 (Th2)-driven. But new cytokines and T cells have been discovered within the last years. In this systematic review, the focus is laid on interleukin-17 (IL-17) and the interleukin-20 (IL-20) family which appear to be fine-tuning the Th2-driven answer.
  
  
  
  IL-17 is a proinflammatory cytokine, which is produced by T cells. Primarily, IL-17 is produced by activated CD4+ cells, called Th-17 cells. IL-17 regulates keratinocyte expression of adhesion molecules and chemokines. IL-17 is involved in the pathogenesis of inflammatory diseases as psoriasis, arthritis, and inflammatory bowel diseases. In allergic diseases, the involvement of the TH17/IL17-pathway has only been recently described. Regarding the IL-20 family, IL-22 is the most interesting and the most studied cytokine in terms of allergic inflammatory disorders. IL-22 is produced by T-helper 22 cells, a new subset of CD4+ cells.
  
  
  
  IL-17 as well as IL-22 seem to play a role in the pathogenesis of allergic skin diseases.
authors.affiliation: Department of Dermatology and Allergy, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Maja A
authors.initials: MA
authors.lastname: Hofmann
authors.forename: Felix
authors.initials: F
authors.lastname: Kiecker
authors.forename: Torsten
authors.initials: T
authors.lastname: Zuberbier
mesh_terms: D000818:Animals; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D007073:Immunoglobulin E / Q000378:metabolism; D007249:Inflammation / Q000276:immunology*; D020381:Interleukin-17 / Q000276:immunology*; D007378:Interleukins / Q000276:immunology*; D015603:Keratinocytes / Q000502:physiology*; D012871:Skin Diseases / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology*
chemical_list: D020381:Interleukin-17; D007378:Interleukins; D007073:Immunoglobulin E; C422042:interleukin 20