Interleukin 13 receptor, alpha 1, also known as IL13RA1/IL-13RA1 and CD213A1 (cluster of differentiation 213A1), is a subunit of the interleukin 13 receptor. IL13RA1 cDNA encodes a 427 amino acid (aa) residue precursor protein with a putative 21 aa residue signal peptide, a 324 aa residue extracellular domain, a 23 aa residue transmembrane region and a 59 aa residue cytoplasmic tail. This subunit together with IL4RA can form a functional receptor for IL13. The lower affinity IL-13 binding protein, previously designated IL-13 R alpha, IL-13 R alpha ' or NR4, is now referred to as IL-13 R alpha 1. The high-affinity IL-13 binding protein, previously also designated IL-13 R or IL-13 R alpha ', is now referred to as IL-13 R alpha 2. IL13RA1 also serves as an alternate accessory protein to the common cytokine receptor gamma chain for interleukin-4 (IL4) signaling, but cannot replace the function of IL2RG in allowing enhanced interleukin-2 (IL2) binding activity.