Interleukin 1 Receptor Type I is a cytokine receptor that belongs to the interleukin-1 receptor family. This protein is a receptor for interleukin alpha (IL1A), interleukin beta (IL1B), and interleukin 1 receptor, type I(IL1R1/IL1RA). It is an important mediator involved in many cytokine induced immune and inflammatory responses. This gene along with interleukin 1 receptor, type II (IL1R2), interleukin 1 receptor-like 2 (IL1RL2), and interleukin 1 receptor-like 1 (IL1RL1) form a cytokine receptor gene cluster in a region mapped to chromosome 2q12.

Both human IL1R gene and  mouse gene containing a single membrane-spanning segment, a large cytoplasmic region, and an extracellular, IL1-binding portion composed of 3 immunoglobulin-like domains.