Box-and Whisker plots: Quantification of myeloid dendritic cells in small airways of never-smokers (n = 11), current smokers without COPD (n = 14), ex-smokers without COPD (n = 14), current smoking COPD patients GOLD stage I&II (n = 23), ex-smoking COPD patients GOLD stage I&II (n = 13) and ex-smoking COPD patients GOLD stage III&IV (n = 10). A-C: DC-SIGN positive intersititial type dendritic cells. D-F: langerin positive Langerhans-type dendritic cells, G-I: BDCA-1 positive dendritic cells and J-L: CD1a positive dendritic cells. Data are presented as number of dendritic cells/area of epithelium, lamina propria or adventitia (cells/mm2). Significant differences between two groups (p values < 0.05), generated by Mann-Whitney-U test after analysis of variance are marked with a full line, p values between 0.05 and 0.08 are marked with a dashed line.