Receptor for interleukin-33 (IL-33); signaling requires association of the coreceptor IL1RAP (PubMed:18450470, PubMed:17675517, PubMed:29045903). Its stimulation recruits MYD88, IRAK1, IRAK4, and TRAF6, followed by phosphorylation of MAPK3/ERK1 and/or MAPK1/ERK2, MAPK14, and MAPK8 (By similarity). Possibly involved in helper T-cell function. Inhibits IL-33 signaling. H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide Interacts with MYD88, IRAK1, IRAK4, and TRAF6 (By similarity). Bound to its ligand IL33, interacts with IL1RAP to form the minimal interleukin-33 signaling complex with a 1:1:1 stoichiometry. Interacts with KIT (bound to KITLG/SCF). A mast cell-specific KITLG/SCF-induced interleukin-33 signaling complex contains IL1RL1, IL1RAP, KIT and MYD88. Interacts with TMED1. Predominantly expressed in hematopoietic tissues, and in macrophage, erythroid, epithelial and fibroblast cell lines. Isoform A is expressed in brain astrocytes and microglia. Isoform B is expressed in brain endothelial cells. Expressed first in the fetal liver and then in lung and hematopoietic tissues. The TIR domain mediates NAD(+) hydrolase (NADase) activity. Self-association of TIR domains is required for NADase activity. Belongs to the interleukin-1 receptor family.