Both eosinophils and IL-5 are critical to the pathogenesis of EGPA, which shows a type 2 inflammatory profile associated with T-helper type 2 (Th2) and T-regulatory cell activity, including increased expression of IL-5, IL-4, and CC motif chemokine receptor 4 [22,23]. The gene discussed is IL4; the disease is eosinophilic granulomatosis with polyangiitis.