Additionally, airway Tregs upregulated influenza infection, IFN-α/β signaling, and IFN-γ signaling pathways, but downregulated IL-2 production, TGF-β, TNF-α, Toll-like receptor (TLR), TCR, and MAPK signaling pathways in COPD (Figure 4I). Here, TGFB1 is linked to chronic obstructive pulmonary disease.