IL13 and asthma: In the developed world, approximately 50% of asthma patients suffer from the allergic phenotype of disease [17] in which type 2 helper T cell (Th2) activation is dominant, resulting in an increased level of Th2 cytokines, such as interleukin (IL)-4, IL-5, and IL-13, a decreased level of Th1 cytokines, such as interferon-gamma (IFN-γ), and an impaired function of regulatory T cells (Tregs).