Demographic characteristics: Bronchoscopy participants.

a p≤0.05—nonsmokers vs. COPD ex-smokers

b p≤0.05—nonsmokers vs. COPD active smokers

c p≤0.05 –COPD ex-smokers vs. COPD active smokers

# GOLD classification is as detailed in the Global Initiative for Chronic Obstructive Lung Disease [24].

Data are expressed as mean±SEM.