IL-18 is a proinflammatory cytokine that can synergize with IL-12 to increase IFN-γ production, NK cell cytotoxity, and Th1 responses, and involves in chronic inflammation, autoimmune diseases, and a variety of cancers. The receptor of IL-18 is a complex of two polypeptide chains, IL-18 receptor 1 (IL-18R1/IL-18Ra/CD218a) and IL-18 receptor accessory protein (IL-18Rap/IL-18 receptor ß/CD218b). Both chain are essential for IL-18 signal transduction. IL-18R1 is a glycosylated membrane protein of 60-100 kDa expressed on variety of cells containing Th1 cells, NK cells, renal epithelial cells and prostate cancer cells. It is a member of IL-1 receptor family and works as ligand binding chain of IL-18R complex.Synonyms: CD218 antigen-like family member A, CDw218a, IL-18 receptor 1, IL-1Rrp, IL1 receptor-related protein, IL1RRP, Interleukin-18 receptor 1