MUC5AC and idiopathic pulmonary fibrosis: Having revealed a greater proportion in both the area and the mucus component of SMGs in IPF patients, we then explored the stained areas of MUC5B, MUC5AC, and CC10 in the surface epithelium of the bronchi, proximal bronchioles, and distal bronchioles (which was replaced by honeycomb cysts in IPF patients), respectively (Figures 2A–C).