The protein encoded by this gene is a member of the interleukin 1 receptor family and is similar to the interleukin 1 accessory proteins. It is most closely related to interleukin 1 receptor accessory protein-like 2 (IL1RAPL2). This gene and IL1RAPL2 are located at a region on chromosome X that is associated with X-linked non-syndromic mental retardation. Deletions and mutations in this gene were found in patients with mental retardation. This gene is expressed at a high level in post-natal brain structures involved in the hippocampal memory system, which suggests a specialized role in the physiological processes underlying memory and learning abilities.