Interleukin-1 family member 8(IL1F8) also known as IL36B, is a member of the interleukin 1(IL-1) cytokine family. IL1F8 may contain a 12-stranded beta-trefoil structure. Until recently, the IL-1 family of cytokines includes four members, with three having pro-inflammatory effects such as IL1F8 and the fourth member being an IL-1 receptor antagonist (IL-1Ra). IL-1 family members exert their effects through binding to receptors that belong to the IL-1 receptor (IL-1R) family. IL1F8 exerts proinflammatory effects in primary human joint cells. Joint and serum IL-1F8 protein levels did not correlate with inflammation, but they were high in some human serum samples tested, including samples from patients with rheumatoid arthritis. IL1F8 also activated NK-κB.