The interleukin 1 receptor accessory protein (IL1RAP) gene, located on human chromosome 3 (191,714,585-191,858,537), encodes a critical co-receptor in IL-1 family signaling networks. It forms heteromeric complexes with ligand-binding receptors (e.g., ST2 for IL-33), facilitating adaptor protein recruitment (e.g., MyD88) to activate NF-κB and MAPK pathways, regulating immune responses and cytokine production. Alternative splicing generates membrane-bound and soluble isoforms; the soluble form modulates inflammation by enhancing ligand-decoy receptor binding. Overexpressed in hematologic malignancies (e.g., acute myeloid leukemia) and solid tumors (e.g., Ewing’s sarcoma), IL1RAP is a promising therapeutic target for CAR-T and antibody-based therapies.