IL9 and allergic asthma: Studies using adoptively transferred models of allergic asthma demonstrated that exogenously or ectopically expressed proallergic cytokines such as TSLP, TNF family cytokine TLI1 (Tnfsf15), and IL-25 promoted airway inflammation by increasing Th9 cell differentiation and IL-9 production [29, 133, 134].