In human IPF lung tissue, we found that MUC5B is co-expressed with surfactant protein C in columnar epithelial cells lining honeycomb cysts (Fig. 1a) and in type 2 alveolar epithelia (Fig. 1b), indicating that cell types involved in lung fibrosis in the distal airspace also express MUC5B. This evidence concerns the gene MUC5B and idiopathic pulmonary fibrosis.