IL9 and asthma: In T2 asthma, the Th2 cytokines IL-4, IL-5, IL-9, IL-13, and IL-25, and the acute proinflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8, subsequently lead to bronchial hyperresponsiveness (BHR), and plasma cells and antibody-producing cells secrete antibodies [20,23].