The proinflammatory cytokine Interleukin 17 (IL-17) is produced by activated T cells to elicit potent cellular responses. IL-17 is secreted as a disulfide-linked homodimeric glycoprotein. A human IL-17 homolog IL-17E is a ligand for EV127/IL-17BR, which is also known as IL-17 receptor homolog 1. IL-17E mRNA is detected at very low levels in several peripheral tissues. IL-17E induces the activation of NFκB and stimulates the production of the proinflammatory chemokine IL-8. In addition, IL-17E has catabolic activity on human articular cartilage. IL-17E is a unique pleiotropic cytokine that may be an important mediator of inflammatory and immune responses. Another homolog of IL-17, IL-17F, is a secreted cytokine expressed only in activated CD4+ T cells and activated monocytes. IL-17F stimulates the production of other cytokines such as IL-6, IL-8 and granulocyte colony-stimulating factor, and regulates cartilage matrix turnover.
