[26]–[30] We chose to examine biomarkers suggestive of macrophage and epithelial cell activation (IL-8, TNF-α, MMP-9 and 12), neutrophilic inflammation (differential cell counts, myeloperoxidase and MMP-9), and injury (fibronectin), each of which have been linked to COPD pathogenesis in previous studies. This evidence concerns the gene CXCL8 and chronic obstructive pulmonary disease.