TNF and chronic obstructive pulmonary disease: The abnormal inflammatory response in the lungs of COPD patients consists of an influx of macrophages, neutrophils, T lymphocytes and increased levels of pro-inflammatory cytokines (e.g. tumour necrosis factor-α [TNF-α], interleukin-8 [IL-8], granulocyte-macrophage colony stimulating factor [GM-CSF])6, chemokines (e.g. monocyte chemoattractant protein-1 [MCP-1] and matrix metalloproteinases (e.g. MMP-1, -9 and -12)6.