CXCL8 and chronic obstructive pulmonary disease: Increased levels of interleukin-8 (IL-8), interleukin-12 (IL-12), tumour-necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1; CCL-2), and macrophage inflammatory protein-1α (MIP-1α; CCL3) have been observed in COPD patients [9,17-21].