CFTR and cystic fibrosis: To study whether confocal reflection microscopy is sensitive to detect changes in ASL height in relation to restoration of CFTR function, primary airway epithelial cell cultures from CF patients with at least one F508del allele (Table 1) were either low temperature corrected by incubation at 27 °C32 or treated with the CFTR corrector VX-809 (lumacaftor) in combination with the potentiator VX-770 (ivacaftor) to improve biosynthesis and function of F508del-CFTR (Fig. 5B, C).