Interleukin 13 is a protein that in humans is encoded by the IL-13 gene. It is a kind of cytokine secreted by many cell types, but especially T helper type 2 (Th2) cells, which is an important mediator of allergic inflammation and disease. The IL-13 gene is mapped to 5q23-q31. IL-13 induces its effects through a multi-subunit receptor that includes the alpha chain of the IL-4 receptor (IL-4Rα) and at least one of two known IL-13-specific binding chains. Furthermore, this gene acts more prominently as a molecular bridge linking allergic inflammatory cells to the non-immune cells in contact with them, thereby altering physiological function.