IL4 and cystic fibrosis: The subsequent addition of CCh transiently increased (P < 0.01) ASL pH, but only in CF-CTRL epithelia treated with IL-4 (ΔASL pH 0.1 ± 0.3, n = 27) compared to CF-CTRL epithelia under normal conditions or IL-4-treated CF-T16AKO epithelia (red trace in Fig. 2C).