The Interleukin 17 (IL-17) family proteins, comprising six members (IL-17, IL-17B through IL-17F), are secreted, structurally related proteins that share a conserved cysteine-knot fold near the C-terminus, but have considerable sequence divergence at the N-terminus. With the exception of IL-17B, which exists as a non‑covalently linked dimer, all IL-17 family members are disulfide-linked dimers. IL-17 family proteins are pro-inflammatory cytokines that induce local cytokine production and are involved in the regulation of immune functions. Two receptors (IL-17 R, and IL-17B R), which are activated by IL-17 family members have been identified. In addition, at least three additional orphan type I transmembrane receptors with homology to IL-17 R, including IL-17 RL (IL-17 RC), IL-17 RD, and IL‑17 RE, have also been reported. Mouse IL-17C cDNA encodes a 194 amino acid (aa) protein with a putative 14 aa signal peptide. Although there are no potential N-linked glycosylation sites, it is reportedly glycosylated. IL-17C shares from 15%‑30% aa sequence identity with other IL-17 family members. Mouse and human IL-17C share 83% aa sequence identity. IL-17C has a very restricted expression pattern and was detected as a rare expressed sequence tag (EST) in an adult prostate and fetal kidney libraries. IL-17C has been shown to stimulate the release of TNF-alpha and IL-1 beta from the monocytic cell line THP-1, a property it shares with IL-17B. Human IL‑17C is active on mouse cells.
