KRT4 and bronchiolitis obliterans syndrome: On the basis of the expression of canonical markers, we found that the proportions of basal cells (KRT14, KRT4, KRT6A, KRT17, KRT5, KRT7, KRT19, and KRT13), club cells (SCGB1A1, SCGB3A1, S100P, MUC13, MUC1, MUC20, and MUC5B), and ciliated cells (FOXJ1, FOXJ2, HYDIN2, CST1, DNAH1, SNTN, OMG, TPPP3, DNAH5, HYDIN, and ERICH3) were greater in the BO group than in the NO group, whereas the proportion of goblet cells (MUC5AC, MUC2, and MUC6) was greater in the NO group than in the BO group in the control group (Fig. S5), which is consistent with the findings of previous studies.