IL13 is an immunoregulatory cytokine produced primarily by activated Th2 cells, and also by mast cells and NK cells. Targeted deletion of IL13 in mice resulted in impaired Th2 cell development and indicated an important role for IL13 in the expulsion of gastrointestinal parasites. IL13 exerts anti-inflammatory effects on monocytes and macrophages and it inhibits the expression of inflammatory cytokines such as IL1beta, TNF-alpha, IL6 and IL8. IL13 has also been shown to enhance B cell proliferation and to induce isotype switching resulting in increased production of IgE. Blocking of IL13 activity inhibits the pathophysiology of asthma. Alternative Names: IL-13 protein, IL13, NC300 protein, IL 13, Human P600 protein, Mouse protein, IL-13, IL-13 protein, IL 13 protein, Interleukin 13 protein