TNF and chronic obstructive pulmonary disease: A study by Guo et al. (2014), in which patients with stable COPD were administered Bufei granules for 12 weeks reported that serum interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β1 after treatment were not significantly different between the two groups (p > 0.05).