Demographic characteristics: Bronchoscopy participants.

<p><sup>a</sup> p≤0.05—nonsmokers vs. COPD ex-smokers</p><p><sup>b</sup> p≤0.05—nonsmokers vs. COPD active smokers</p><p><sup>c</sup> p≤0.05 –COPD ex-smokers vs. COPD active smokers</p><p><sup>#</sup> GOLD classification is as detailed in the Global Initiative for Chronic Obstructive Lung Disease [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134209#pone.0134209.ref024" target="_blank">24</a>].</p><p>Data are expressed as mean±SEM.</p>