IL-13–induced goblet cell metaplasia has been noted to contribute to airway remodeling and pathological mucus hypersecretion in asthma, and IL-13 has been found to promote susceptibility and abrogate acquired immunity to Leishmania major infection, possibly by acting as a Th2 cytokine and downregulating Th1 cytokines such as IFN-γ (30). This evidence concerns the gene IFNG and asthma.