TNF and chronic obstructive pulmonary disease: Lung inflammation associated with COPD leads to an elevation in various biomarkers indicative of neutrophilic inflammation (neutrophils, elastase, MMP9, calprotectin, and neutrophils found in bronchoalveolar lavage) along with increased pro-inflammatory cytokines (C-reactive protein, TNF-α, IL-6, IL-1β, and IFNα within peripheral blood) [121].