IL-17E (IL-25)

Alias: Interleukin 17E, Interleukin-25

IL-17E (IL-25) was identified as an IL-17 family member based on its sequence homology, though it was originally believed to be a TH2 cytokine based on the detection of mRNA transcripts in polarized TH2 cells. Its expression was later observed in epithelial cells, eosinophils, and mast cells. IL-17E is now known to be produced by mucosal epithelial cells as well as many immune cell types that include TH2, mast cells, macrophages, eosinophils, and NKT cells. Once secreted, IL-17E is known to bind to the receptors IL-17RA and IL-17RB (IL-25R) and activate the NFκB pathway where it is involved as a TH2 cell-promoting cytokine. IL-17E is believed to both induce TH2 cell differentiation and responses with the upregulation of such TH2 cytokines as IL-4, IL-5, and IL-13. IL-17E also suppresses TH17 cell responses and development by the induction of IL-13 in dendritic cells or by inhibiting IL-23 production in macrophages. Administration of IL-17E also promotes symptoms of allergic asthma, such as eosinophil infiltration, airway hyper-reactivity, and high circulating levels of IgE.