TGFB1 and pulmonary fibrosis: Finally, the results that increased IL‐1β and TGF‐β1 in AT2 pneumocytes and epithelial cells either in old mice or in mice exposed to hypoxia is inhibited in arg‐ii−/− animals, reinforce our conclusion and may represent an explanantion of hypoxia‐associated lung fibrosis (Gille et al., 2018; Lee et al., 2019).