Six interleukin-17 (IL-17)-family (IL-17A-IL-17F) and five IL-17 receptor (IL-17R)-family (IL-17RA-IL-17RE) members have been reported in mammalian cells. IL-17RA (known as IL-17R, IL-17AR, CD217) is a 128-158 kD type I transmembrane glycoprotein. IL-17R binds to IL-17A (also known as IL-17, and CTLA-8, is a hallmarker of Th17 cells) and IL-17F and mediates the proinflammatory signals through interaction with IL-17RC or IL-17RD. IL-17R has broad tissue distribution, including fibroblasts, epithelial cells, endothelial cells, stromal cells, B cells, T cells, NK cells, monocytes and granulocytes.