Background: Bronchial mucosal dendritic cells (DCs) initiate and regulate immune responses to inhaled antigens, viruses and bacteria. Currently, little is known of their numbers in patients with chronic obstructive pulmonary disease (COPD). While reductions in their numbers have been reported recently in smokers with asthma, nothing is known of the effects of cigarette smoking on bronchial DCs in COPD. The present study compares DC numbers in current and ex-smokers with COPD. Methods: Endobronchial biopsies were obtained from 15 patients with moderate to severe COPD [10 current smokers (median FEV1 45.5 [range 23-68] %)& 5 ex-smokers (median FEV1 30 [range 21-52] % of predicted], 11 non-smoker asthmatics (median FEV1 102 [range 89-116] %) and 11 non-smoker healthy controls (median FEV1 110 [range 92-135] %). We applied transmission electron microscopy (TEM) in order to identify the total population of DCs by their ultrastructure and counted them in both epithelium and subepithelium. Results: DC numbers (median & range) were significantly lower in current smokers with COPD at 0.0 (0.0-156.8) cells/mm2 in the epithelium and 4.5 (0.0-63.6) cells/mm2 in the subepithelium compared with ex-smokers with COPD that had 97.9 (93.5-170.3) cells/mm2 in their epithelium (p < 0.05) and 91.8 (38.2-283.3) cells/mm2 in their subepithelium (p < 0.01). DCs numbers in ex-smokers with COPD were similar to those in the atopic asthmatics and in the healthy controls: i.e. for the latter 131.6 (33.3-235.5) cells/mm2 in the epithelium and 64.4 (0.0-182.4) cells/mm2 in the subepithelium. Conclusions: In COPD, bronchial mucosal DC numbers are fewer in current smokers than in those who had quit smoking. In the latter, DC numbers are similar to non-smoking asthmatics and non-smoking healthy controls. The functional consequences of the reduction in mucosal DC numbers in smokers with COPD have yet to be determined.
- dendritic cell