IL4 Receptor alpha (IL4RA) is the alpha chain of the interleukin 4 receptor which binds to both interleukin 4 and interleukin 13 to regulate IgE production, chemokine and mucus production at sites of allergic inflammmation. The IL4 response is involved in promoting Th2 differentiation. The secreted extracellular domain of IL4R alpha, called sIL4R alpha, can inhibit IL4-mediated cell proliferation and IL5 upregulation by T-cells. It has no signaling abilities. Allelic variations in the IL4RA gene have been associated with atopy, a condition that can manifest itself as allergic rhinitis, sinusitus, asthma, or eczema.