The function of IL1RL1 (interleukin 1 receptor like 1, ENSG00000115602) is as follows. Receptor for interleukin-33 (IL-33) which plays crucial roles in innate and adaptive immunity, contributing to tissue homeostasis and responses to environmental stresses together with coreceptor IL1RAP (PubMed:35238669). Its stimulation recruits MYD88, IRAK1, IRAK4, and TRAF6, followed by phosphorylation of MAPK3/ERK1 and/or MAPK1/ERK2, MAPK14, and MAPK8. Possibly involved in helper T-cell function (Probable) (PubMed:16286016). Upon tissue injury, induces UCP2- dependent mitochondrial rewiring that attenuates the generation of reactive oxygen species and preserves the integrity of Krebs cycle required for persistent production of itaconate and subsequent GATA3- dependent differentiation of inflammation-resolving alternatively activated macrophages (By similarity). {ECO:0000250|UniProtKB:P14719, ECO:0000269|PubMed:16286016, ECO:0000269|PubMed:35238669, ECO:0000305|PubMed:19836339}. [Isoform B]: Inhibits IL-33 signaling. .