IL9R (Interleukin 9 Receptor) is a Protein Coding gene. The protein encoded by this gene is a cytokine receptor that specifically mediates the biological effects of interleukin 9 (IL9). IL9 is involved in mast cell maturation and the enhancement of IgE production by B cells. Furthermore, linkage data in the human and mice have suggested that IL9 may contribute to asthma. The ligand binding of this receptor leads to the activation of various JAK kinases and STAT proteins, which connect to different biologic responses. IL9R is known to be autosomal in mice and is X-linked only in primates. The more recent X linkage and more telomeric position of the IL9R gene may explain its autosomal, 'un-inactivated' transcriptional status.