TNF and chronic obstructive pulmonary disease: Additionally, increased serum TNF-α was shown in COPD patients compared with smokers (54.32±3.52 vs. 21.35±1.73 pg/mL, P<0.0001) and nonsmokers (54.32±3.52 vs. 13.90±0.77 pg/mL, P<0.0001) (Fig 2C).