Within the IL18 receptor complex, does not mediate IL18-binding, but involved in IL18-dependent signal transduction, leading to NF-kappa-B and JNK activation (PubMed:11046021, PubMed:15843532, PubMed:9792649). May play a role in IL18-mediated IFNG synthesis from T-helper 1 (Th1) cells (By similarity). H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide Forms a ternary complex with IL18 and IL18R1. Within this complex, IL18R1 is involved in ligand-binding and IL18RAP in signaling leading to NF-kappa-B and JNK activation. The TIR domain mediates NAD(+) hydrolase (NADase) activity. Self-association of TIR domains is required for NADase activity. Impaired IL-18 signaling. Belongs to the interleukin-1 receptor family.