HMOX1 and hypersensitivity pneumonitis: Reduced the levels of caspase-3, IL-1β, TNF-α, TGF-β, HYP, 3-NT, and 4-HNE; increased the levels of Nrf2, HO−1, NQO1, SOD1, and CAT; alleviated BLM-induced alveolar epithelial cell apoptosis, alveolitis, collagen accumulation, lung oxidative stress, and lung fibrosis.