The role of interleukin-1 receptor antagonist in the prevention and treatment of disease

 Interleukin-1 (IL-1) and tumor necrosis factor α (TNF-α) play key proinflammatory roles in a variety of human diseases, including rheumatoid arthritis (RA). IL-1 receptor antagonist (IL-1Ra) is a naturally occurring structural variant of IL-1 that competitively inhibits receptor binding of IL-1. Four forms of IL-1Ra have been described: secretory IL-1Ra (sIL-1Ra) and three intracellular molecules (icIL-1Ra1, 2, and 3). Excess amounts of IL-1Ra are necessary to inhibit the biological effects of IL-1. The endogenous production of IL-1Ra plays an anti-inflammatory role, but the level of production of IL-1Ra in inflamed tissues may not be adequate to block IL-1 effectively. An allelic polymorphism in the IL-1Ra gene is associated with a variety of human diseases, largely of epithelial or endothelial cell origin. The disease associated allele IL1RN^*2 may lead to a decreased production of icIL-1Ra1 by these cells, predisposing the patient to an imbalance in the IL-1 system. The therapeutic administration of IL-1Ra was found to be safe and efficacious in the treatment of RA. Intraarticular delivery of the IL-1Ra cDNA by ex vivo gene therapy in patients with RA was effective in enhancing local IL-1Ra production. This unique form of therapy is under further evaluation. Correspondence to:W.P. Arend