IL9 and cystic fibrosis: Stimulation with Th2 cytokines IL-4, IL-9, and IL-13 significantly increased the hCLCA1 protein expression (P < 0.05) in mucosal tissue explant from the CF patient upper airways, while MUC5AC mRNA and mucin protein levels were not significantly altered, which questioned the role of hCLCA1 as a mediator of mucus hypersecretion in CF.51