CFTR and cystic fibrosis: Figure 3 depicts the ICM tracing from one F508del/F508del subject (male, age 37 years, sweat Cl- = 113 mMol, pancreatic insufficient, FEV1 = 63%) showing features of functional CFTR, including a clear Cl- upward deflection following stimulation with forskolin/IBMX (compare with non-CF result in Figure S1 in File S1). The total change in Isc produced by forskolin/IBMX+carbachol was 15.8% of the mean wtCFTR response (non-CF subjects).