Lung fibroblast activation is considered to be a major mechanism of pulmonary fibrosis (Suzuki et al., 2020; Wynn & Ramalingam, 2012), and data in this current study indicated that the number of lung fibroblasts was lower in Dpp4 deficient mice with BLM‐induced pulmonary fibrosis than that in WT mice (Figure 3g). This evidence concerns the gene DPP4 and pulmonary fibrosis.