IL-1Rrp is a novel receptor-like molecule similar to the type I interleukin-1 receptor and its homologues T1/ST2 and IL-1R AcP.

A novel member of the interleukin-1 receptor family has been cloned by polymerase chain reaction using degenerate oligonucleotide primers derived from regions of sequence conservation, using as template a yeast artificial chromosome known to contain both interleukin-1 (IL-1) receptors and T1/ST2. The new receptor, called IL-1 receptor-related protein or IL-1Rrp, fails to bind any of the known IL-1 ligands. A chimeric receptor, in which the IL-1Rrp cytoplasmic domain is fused to the extracellular and transmembrane regions of the IL-1 receptor, responds to IL-1 following transfection into COS cells by activation of NFkappaB and induction of IL-8 promoter function.