IL1rn also known as Interleukin-1 receptor antagonist protein is a member of the interleukin 1 cytokine family. IL1rn may represent a reservoir of IL-1 inhibitors, released upon cell death, whose function is no limit the pro-inflammatory signals but most prominently by mononuclear phagocytes and keratinocytes. IL1rn is reported to be associated with increased risk of osteoporotic fractures and gastric cancer. Recombinant rat IL1rn, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.