Note that single-cell functional enrichment of the MHC class I antigen presentation pathway was highly correlated with those of negative regulation of the cell cycle and IFN-γ-mediated signaling pathway among all 4 types of airway epithelial cells (Fig. 5B and Fig. S5D–S5F), strongly suggesting a potential association between autoimmune susceptibility as well as IFN reactivity and cellular senescence of epithelial cells and COPD pathology. Here, IFNG is linked to chronic obstructive pulmonary disease.