TNF and chronic obstructive pulmonary disease: The number of recognized triggers for NET formation in in vitro systems is vast and includes proinflammatory cytokines (CXCL8 and TNF-α), bacterial products (formylated peptides and LPS), bacteria (P aeruginosa and Haemophilus influenzae), fungi, activated platelets, and rheumatoid factor (immunoglobulin).11, 23, 29, 31, 33, 34, 35, 36 Evaluating the drivers of NET formation in patients with COPD is challenging because the majority of these proposed drivers are present in the airways of patients with COPD under normal conditions.5