TGFB1 and chronic obstructive pulmonary disease: We further evaluated the concentrations of IL-1β, IL-6, IL-23, and TGFβ1 in HC, HS, COPD patients and found that concentrations of IL-1β, IL-6, and IL-23 in patients with COPD were much higher than those in HC and HS; however, the level of TGFβ1 was significantly decreased in patients with AECOPD (Figure 6B).