Interleukin 18 （IL-18） is a member of the IL-1 family of cytokines and shares numerous immunoregulatory functions with IL-12. The functional IL-18 receptor complex consists of two subunits: IL-18Rα （also known as IL-1R5 or IL-1Rrp） and IL-18Rβ （also known as IL-1R7 or AcPL）. Both subunits belong to the IL-1 receptor superfamily. IL-18R is widely expressed in various tissues, including the spleen, thymus, leukocytes, liver, lung, heart, small and large intestines, prostate, and placenta.
The IL-18 receptor complex is responsible for binding the pro-inflammatory cytokine IL-18, but not IL-1α or IL-1β. It is involved in IL-18-mediated IFNγ synthesis from T-helper 1 （Th1） cells and contributes to IL-18-induced cytokine production, either independently of SLC12A3 or as a complex with SLC12A3.