CFTR and cystic fibrosis: In the lungs of patients with CF, deficient CFTR-mediated chloride and fluid secretion results in liquid depletion on the airway surface, which causes dehydration/hyperconcentration of the mucus layer representing a key mechanism leading to impaired mucociliary clearance that sets the stage for airway mucus plugging, chronic bacterial infection and inflammation, and progressive lung damage (2–4).