It is now well established in cystic fibrosis (CF) that a lack of functional cystic fibrosis transmembrane conductance regulator (CFTR) impairs airway bicarbonate and fluid secretion producing an acidic, viscous ASL [1], [2], [3] that is readily colonised by bacteria such as Pseudomonas aeruginosa[4]. The gene discussed is CFTR; the disease is cystic fibrosis.