Upon activation, TH2 cells produce and secrete a wide range of cytokines that cause mucosal mastocytosis (IL-9), eosinophilia (IL-5) (53), airway hyperreactivity and mucus hyperproduction (IL-13) (54), as well as isotype switching in IgG-producing B cells to allergen-specific IgE-producing cells (IL-4 and IL-13) (55). The gene discussed is IL13; the disease is Increased total eosinophil count.