Interleukin-1 receptor antagonist.
IL-1ra is the first described naturally occurring receptor antagonist of any cytokine or hormone-like molecule. IL-1ra is a member of the IL-1 family by three criteria: amino acid sequence homology of 26 to 30% to IL-1 beta and 19% to IL-1 alpha; similarities in gene structure; and common gene localization to human chromosome 2q14. Two structural variants of IL-1ra exist: sIL-1ra, a secretory molecule produced by monocytes, macrophages, neutrophils, fibroblasts, and other cells; and icIL-1ra, an intracellular molecule produced by keratinocytes and other epithelial cells, macrophages, and fibroblasts. IL-1ra production by monocytes, macrophages, and neutrophils may be regulated in a differential fashion with IL-1 beta. Human IL-1ra binds to both human IL-1RIs and IL-1RIIs on cell surfaces, although with 100-fold greater avidity to IL-1RIs. IL-1ra may bind preferentially to soluble IL-1RIs and not at all to soluble IL-1RIIs. IL-1ra competitively inhibits binding of both IL-1 alpha and IL-1 beta to cell surface receptors without inducing any discernible intracellular responses. All three forms of IL-1 may bind to IL-1 receptors in a similar fashion but IL-1ra may lack the secondary interactions necessary to trigger cell responses. A 100-fold or greater excess of IL-1ra over IL-1 may be necessary to inhibit biological responses to IL-1 both in vitro and in vivo. The roles of sIL-1ra and icIL-1ra in normal physiology or in host defense mechanisms remain unclear. The administration of IL-1ra blocks the effects of IL-1 in some animal models of septic shock, inflammatory arthritis, graft-versus-host disease, and inflammatory bowel disease. The preliminary results of clinical trials in humans indicate possible efficacy of IL-1ra in sepsis syndrome, rheumatoid arthritis, and GVHD.
Department of Medicine, University of Colorado Health Sciences Center, Denver 80262.
W P
WP
Arend
D000818:Animals; D002874:Chromosome Mapping; D006801:Humans; D007107:Immune System / Q000187:drug effects; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000494:pharmacology / Q000627:therapeutic use
C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins