As a result of these roles, the IL-17 family has been linked to many immune/autoimmune related diseases including rheumatoid arthritis, asthma, lupus, allograft rejection, anti-tumour immunity and recently psoriasis, multiple sclerosis, and intracerebral hemorrhage. IL-17 function is also essential to a subset of CD4+ T-Cells called T helper 17 (T h17) cells. The increased expression of chemokines attracts other cells including neutrophils but not eosinophils. The release of cytokines causes many functions, such as airway remodeling, a characteristic of IL-17 responses. IL-17 acts with IL-22 (produced mainly by T helper 22 cells in humans, but by T helper 17 cell in mice) to induce expression of antimicrobial peptide by keratinocytes. IL-17 induces the production of many other cytokines (such as IL-6, G-CSF, GM-CSF, IL-1β, TGF-β, TNF-α), chemokines (including IL-8, GRO-α, and MCP-1), and prostaglandins (e.g., PGE 2) from many cell types ( fibroblasts, endothelial cells, epithelial cells, keratinocytes, and macrophages). IL-17 is commonly associated with allergic responses. The most notable role of IL-17 is its involvement in inducing and mediating proinflammatory responses. Numerous immune regulatory functions have been reported for the IL-17 family of cytokines, presumably due to their induction of many immune signaling molecules. For instance, the sequence homology between the corresponding human and mouse proteins is usually between 62–88%. In mammals, the sequences of these cytokines are highly conserved. Among IL-17 family members, the IL-17F isoforms 1 and 2 (ML-1) have the highest sequence homology with IL-17A (55 and 40%, respectively). To the reference, the members of the IL-17 family do not exhibit a significant sequence homology with other cytokines. These conserved cysteine residues are critical to the right 3-dimensional shape of the entire protein molecule. Their protein sequences contain four highly conserved cysteine residues. All members of the IL-17 family have a similar protein structure. The IL-17 family in humans comprises IL17A (sometimes confusingly called "IL-17"), IL17B, IL17C, IL17D, IL17E and IL17F. Moreover, an activation of IL-17 signalling is often observed in the pathogenesis of various autoimmune disorders, such as psoriasis. Promoting the inflammation, IL-17 acts in concert with tumor necrosis factor and interleukin-1. Typically, the signaling events mentioned above follow an invasion of the body by pathogens. Acting as chemoattractants, these chemokines recruit the immune cells, such as monocytes and neutrophils to the site of inflammation.
After binding to the receptor, IL-17 activates several signalling cascades that, in turn, lead to the induction of chemokines. In turn, there are at least three variants of IL-17R referred to as IL17RA, IL17RB, and IL17RC. The biologically active IL-17 interacts with type I cell surface receptor IL-17R. In rodents, IL-17A is often referred to as CTLA8. IL17A protein exhibits a high homology with a viral IL-17-like protein ( O40633) encoded in the genome of T-lymphotropic rhadinovirus Herpesvirus saimiri. The protein encoded by IL17A is a founding member of IL-17 family (see below). who isolated IL17A transcript from a rodent T-cell hybridoma. Originally, Th17 was identified in 1993 by Rouvier et al. They are produced by a group of T helper cell known as T helper 17 cell in response to their stimulation with IL-23. Interleukin 17 family ( IL17 family) is a family of pro-inflammatory cystine knot cytokines. Interleukin 17 familyĬrystallographic structure of dimeric human IL-17f. This article is about the protein family.