Interleukin 17C (IL-17C) is a glycosylated 179 amino acid cytokine (molecular weight 20 kDa) which is expressed as a disulfide linked dimer. IL-17C is member of a family of structurally related proteins (IL-17A – IL-17F) which play pivotal roles in inflammatory and immunoregulatory responses. In contrast to other members of the family IL-17C is expressed primarily in non-lymphoid cells such as keratinocytes and epithelial cells. It binds to the receptor IL- 17RE which is expressed on TH-17 cells. This cytokine is thought to play important role in TH-17 mediated autoimmunity by stimulating the production of IL-17A, IL-22 and MIP-3α.