IL-1 Receptor Type II Charles A. Dinarello* Department of Infectious Diseases, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, B168, Denver, CO 80262, USA * corresponding author tel: 303-315-3589, fax: 303-315-8054, e-mail:
[email protected]aol.com DOI: 10.1006/rwcy.2000.15003. SUMMARY Structure The extracellular domains of type II IL-1R are structurally related to those of the type I IL-1R; however, the type II IL-1R is a decoy receptor in that the primary ligand, IL-1 , preferentially binds to this receptor rather than the signaling receptor. As such, in the presence of increasing expression of the type II receptor on the cell surface, less IL-1 signaling takes place. This is because the type II IL-1R lacks a cytoplasmic domain capable of cell signal transduction. The type II IL-1R also exists in a shed form as a soluble receptor. The soluble receptor has a high affinity to bind IL-1 over that of IL-1 or IL-1Ra. The soluble IL-1R type II is ideally su