In the case of radioactive lung injury, alveolar macrophages can release synthetic TGF − β1 normal fibroblast phenotype transformation, thus fibroblasts' constant division, proliferation, differentiation, and maturation, and synthesis of collagen, the abnormal pulmonary interstitial collagen ingredients increased, and thus promoted the occurrence of pulmonary fibrosis; at the same time, TGF − β1 can also accelerate lung radiation injury by stimulating monocytes and inflammatory cells in the area of lung injury to release cytokines such as TNF − α and TNF − β1. The gene discussed is TNF; the disease is pulmonary fibrosis.