Interleukin 1 receptor-like 1 (IL1RL1) is also known as ST2, DER4, FIT-1, IL33R, ST2L, ST2V, which belongs to the interleukin-1 receptor family. IL1RL1 contains three Ig-like C2-type (immunoglobulin-like) domains and one TIR domain. IL1RL1 is receptor for interleukin-33 (IL-33), its stimulation recruits MYD88, IRAK1, IRAK4, and TRAF6, followed by phosphorylation of MAPK3/ERK1 and/or MAPK1/ERK2, MAPK14, and MAPK8. IL1RL1 possibly involved in helper T-cell function. IL1RL1 can interact with MYD88, IRAK1, IRAK4, and TRAF6.