TNF and chronic obstructive pulmonary disease: Compared with the non-COPD subjects, the COPD patients showed higher levels of circulating inflammatory cytokines and destructive mediators including C-reactive protein (CRP), interleukin (IL)-8, tumor necrosis factor (TNF) α, and matrix metalloproteinase (MMP) (Barnes and Celli, 2009; Sinden and Stockley, 2010).