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.a p≤0.05：非吸烟者与慢性阻塞性肺疾病（COPD）既往吸烟者组间比较 b p≤0.05：非吸烟者与COPD现吸烟者组间比较 c p≤0.05：COPD既往吸烟者与COPD现吸烟者组间比较 # GOLD分级详见《慢性阻塞性肺疾病全球倡议（Global Initiative for Chronic Obstructive Lung Disease）》[24]。 数据以均值±标准误（standard error of the mean，SEM）表示。