Interleukin-1 receptor (IL-1R) is a protein that binds to interleukin-1. There are two forms of IL-1R: the type I receptor (IL-1RI) is primarily responsible for transmitting the inflammatory effects of interleukin-1 (IL-1) while type II receptor (IL-1RII) may act as a suppressor of IL-1 activity by competing for IL-1 binding. The IL-1 receptor accessory protein (IL1RAP) is a transmembrane protein that interacts with IL-1R and is required for IL-1 signal transduction. Interleukin-1 receptor (IL-1RI) has three immunoglobulin-like domains. The first and second immunoglobulin domains form a conserved binding site, and its third domain shows flexibility within a certain range. IL-1, IL-1R and IL-1 receptor accessory protein (IL1RAP) form a functional signaling receptor complex, which triggers downstream signaling pathways to produce physiological responses.