IL4 and allergic asthma: In fact, allergic asthma, or type 2 immune response, is now considered as a complex network between type 2 cytokines (IL-4, IL-5, IL-9, and IL-13), which are mainly secreted from Th2 cells, IgE-producing B cells, group 2 innate lymphoid cells (ILC-2), and a small fraction of IL-4-producing NK cells and NK-T cells, basophils, eosinophils, mast cells, and alarmins (IL-25, IL-33, and TSLP), which are released from tissue cells, particularly epithelial cells (12).