PDCD1 and interstitial lung disease: (2) Focusing on molecular mechanisms: moreover, the crosstalk of HIF-1 and nuclear factor κB signaling pathways of PDT that can both affect molecular expression and immunologic function in hypoxia is thought-provoking [33]; the distinct regulation of HIF-1 or PD-1/PD-L1 pathway in pulmonary fibrogenesis and carcinogenesis deserves attention, which may contribute to the development of individual manangment in interstitial lung disease and lung cancer [34, 35].