DPP4 and pulmonary fibrosis: In the present study, lung injury parameters of protein concentrations and the number of neutrophils in BALF 21 days after BLM treatment demonstrated no significant differences between Dpp4 KO and WT mice (Figure 2), suggesting that neutrophilic inflammation is not associated with the amelioration of fibrosis in Dpp4 deficiency in the fibrotic stage of BLM‐induced lung fibrosis.