Inhibits the activity of interleukin-1 by binding to receptor IL1R1 and preventing its association with the coreceptor IL1RAP for signaling. Has no interleukin-1 like activity. Binds functional interleukin-1 receptor IL1R1 with greater affinity than decoy receptor IL1R2; however, the physiological relevance of the latter association is unsure. {ECO:0000269|PubMed:7775431}.,Alternative sequence (3); Beta strand (13); Chain (1); Disulfide bond (1); Glycosylation (1); Helix (3); Natural variant (1); Signal peptide (1); Turn (3),The intracellular form of IL1RN is predominantly expressed in epithelial cells.,Microvascular complications of diabetes 4 (MVCD4) [MIM:612628]: Pathological conditions that develop in numerous tissues and organs as a consequence of diabetes mellitus. They include diabetic retinopathy, diabetic nephropathy leading to end-stage renal disease, and diabetic neuropathy. Diabetic retinopathy remains the major cause of new-onset blindness among diabetic adults. It is characterized by vascular permeability and increased tissue ischemia and angiogenesis. {ECO:0000269|PubMed:8786086}. Note=Disease susceptibility is associated with variations affecting the gene represented in this entry.; Interleukin 1 receptor antagonist deficiency (DIRA) [MIM:612852]: A rare autoinflammatory disease of skin and bone resulting in sterile multifocal osteomyelitis, periostitis, and pustulosis from birth. The term autoinflammatory disease describes a group of disorders characterized by attacks of seemingly unprovoked inflammation without significant levels of autoantibodies and autoreactive T-cells. {ECO:0000269|PubMed:19494218}. Note=The disease is caused by mutations affecting the gene represented in this entry.