Asthma can be broadly differentiated into type 2 (T2) and non-T2 asthma and patients with T2 asthma show increased numbers of eosinophils, T helper 2 cells (TH2), innate lymphoid cells 2 (ILC2) and augmented secretion of interleukin (IL)-4, IL-5, and IL-13 into the airways as well as increased levels of immunoglobulin E (IgE) in the serum [27–30], (Fig. 2). Here, IL4 is linked to asthma.