Interleukin 17 family (IL17 family) is a family of pro-inflammatory cystine knot cytokines. They are produced by a group of T helper cell known as T helper 17 cell in response to their stimulation with IL-23. Originally, Th17 was identified in 1993 by Rouvier et al. who isolated IL17A transcript from a rodent T-cell hybridoma. The protein encoded by IL17A is a founding member of IL-17 family (see below). IL17A protein exhibits a high homology with a viral IL-17-like protein (O40633) encoded in the genome of T-lymphotropic rhadinovirus Herpesvirus saimiri. In rodents, IL-17A is often referred to as CTLA8.The biologically active IL-17 interacts with type I cell surface receptor IL-17R. In turn, there are at least three variants of IL-17R referred to as IL17RA, IL17RB, and IL17RC. After binding to the receptor, IL-17 activates several signalling cascades that, in turn, lead to the induction of chemokines. Acting as chemoattractants, these chemokines recruit the immune cells, such as monocytes and neutrophils to the site of inflammation. Typically, the signaling events mentioned above follow an invasion of the body by pathogens. Promoting the inflammation, IL-17 acts in concert with tumor necrosis factor and interleukin-1. Moreover, an activation of IL-17 signalling is often observed in the pathogenesis of various autoimmune disorders, such as psoriasis.