Immunohistochemistry for EMT biomarkers in small airways epithelium of patients with chronic obstructive pulmonary disease (COPD). Small airways sections from non-smokers (n = 25), smokers (n = 25), non-smokers with COPD (n = 10), and smokers with COPD (n = 18) were immunostained. (A) Epithelial marker E-cadherin (brown) and mesenchymal marker vimentin (brown) staining are observed in small airways epithelium from a non-smoker and a patient with COPD with serial sections. Black arrows show the main distribution of the positive immunostaining regions. (B) Mesenchymal marker vimentin (brown) from non-smokers (a), smokers (b), non-smokers with COPD (c) and smokers with COPD (d). (C) Quantification of mesenchymal marker vimentin positive cells in the small airways epithelium. The number of positive epithelial cells per mm reticular basement membrane (Rbm) in small airways. P values in figure were obtained by Mann–Whitney U test analyses. Images were obtained using a 100 × oil-immersion objective.