Levels of TNF-α (pg/ml), expressed as median values (inter-quartile range) in induced sputum of healthy non-smokers (A), asymptomatic smokers (B) and COPD smokers (C)

<p><b>Copyright information:</b></p><p>Taken from "Vascular endothelial growth factor: an angiogenic factor reflecting airway inflammation in healthy smokers and in patients with bronchitis type of chronic obstructive pulmonary disease?"</p><p>http://respiratory-research.com/content/8/1/53</p><p>Respiratory Research 2007;8(1):53-53.</p><p>Published online 15 Jul 2007</p><p>PMCID:PMC1939848.</p><p></p> *p < 0.05, for healthy non-smokers vs COPD smokers