The protein encoded by this gene is an accessory subunit of the heterodimeric receptor for IL18. This protein enhances the IL18 binding activity of IL18R1 (IL1RRP), a ligand binding subunit of IL18 receptor. The coexpression of IL18R1 and this protein is required for the activation of NF-kappaB and MAPK8 (JNK) in response to IL18. [provided by RefSeq, Jul 2008]