Notably, in the surface epithelium of distal bronchioles, we found a significantly lower CC10 expression of secretory cells in IPF patients as compared to that of control subjects (p < 0.001, Figure 2F), indicating that the major secretory cell type of CC10+MUC5B−MUC5AC− in the distal bronchioles of control subjects has been commonly replaced by MUC5B+CC10−MUC5AC− cells in honeycomb cysts of IPF patients (Figures 2A–C). Here, MUC5B is linked to idiopathic pulmonary fibrosis.