Immune cells in COPD and emphysema exhibit T helper 1 (Th1)/Th17 polarization, decreased programmed death ligand-1 (PD-L1) expression in alveolar macrophages, and increased production of interferon (IFN)-γ by CD8+ T cells56, a phenotype believed to prevail at tumor initiation, whereas established tumors are dominated by Th2/M2-like macrophages57. This evidence concerns the gene IFNG and chronic obstructive pulmonary disease.