CFTR and cystic fibrosis: Indeed, while a plateau of Cl− transport is reached when 10–50% of cells express CFTR (Dannhoffer et al., 2009), explained by a limitation in Cl− entry into cells at the basolateral membrane, a 50:50 mix of CF and non-CF porcine epithelial cells transported HCO3− at half the rate of non-CF epithelia (Shah et al., 2016a).