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Interleukin 13 (IL-13) is a cytokine important in type 2 immune responses and is expressed by T helper type 2 (Th2) cells and group 2 innate lymphoid cells (ILC2s) (Pulendran & Artis). IL-13 binds a receptor composed of IL-4Ra and IL-13Ra1 or IL-13Ra2 (Wynn 2003). IL-13 receptor is expressed on B cells and promotes B cell proliferation, induces class switching to IgG4 and IgE, and functions in the recruitment and activation of IgE-producing B cells (Hershey). The receptor is also expressed on basophils, eosinophils, mast cells, endothelial cells, fibroblasts, monocytes, macrophages, respiratory epithelial cells, and smooth muscle cells (Hershey). Signaling through the IL-13 receptor activates the JAK/STAT and IRS-1/IRS-2 pathways. In vivo, IL-13 has a role in resistance to extracellular helminth parasites by regulating gastrointestinal parasite expulsion, as well as in airway hyperresponsiveness, allergic inflammation, tissue remodeling, tumor cell growth, and fibrosis (Wynn 2015). Secreted IL-13 is a protein consisting of 112 amino acids with a molecular mass of 10 kDa (Hershey). Human IL-13 is not species-specific but has greater activity on human cells compared to mouse cells (Hershey).