Airway dendritic cells (DCs) play a key role in smoke-related lung diseases; however, the acute effects of tobacco smoke on human airway DCs in vivo are unknown.

A total of 16 smokers underwent bronchoalveolar lavage at two time-points: directly after a 4-h period of nonsmoking (no smoke exposure); and directly after a 4-h period during which eight cigarettes were smoked (acute smoke exposure). Using flow cytometry, myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), as well as function-associated surface molecules on mDCs, were analysed in bronchoalveolar lavage fluid (BALF) and in blood.

The numbers of macrophages, lymphocytes, neutrophils, eosinophils and pDCs were unchanged in BALF following acute smoke exposure, as compared to no smoke exposure. In contrast, there was a strong increase in mDC number in BALF and a concomitant decrease in mDC number in blood following acute smoke exposure. In addition, acute smoke exposure led to an increase in the expression of the surface molecules blood dendritic cell antigen 1 and 4 and a decrease in the expression of the lung homing receptor, CC chemokine receptor 5, on mDCs in BALF.

Acute tobacco smoke inhalation results in an immediate and selective recruitment of mDCs into human airways, which might reflect the very early reaction of the adaptive immune system to smoke exposure.