Comparative analysis of dendritic cell numbers and subsets between smoking and control subjects in the peripheral blood.

It has been well known that smoking alters the property and functionality of a wide range of immune cells including dendritic cells (DCs). However, a great deal of effort in the past has been mainly devoted to dissect the effect of smoking on pulmonary DCs, while its exact impact on circulating DCs remains to be fully addressed. Therefore, in the present report we particularly examined the impact of smoking on the number and subset of DCs in the peripheral blood by multi-parametric flow cytometry analysis. A significant increase for peripheral blood mononuclear cells (PBMCs) was noted in the smoking subjects. Subsequent studies revealed that the percentage for plasmacytoid DCs (pDCs) and total DCs in PBMCs was significantly higher in the smoking subjects as compared with that of control subjects, while the percentage for myeloid DCs (mDCs) did not differ between two groups. It was also found that the absolute number for total DCs, mDCs and pDCs were significantly higher in the smoking subjects than that of control subject. However, the mDC/pDC ratio was significantly reduced, suggesting that smoking impairs the balance of DC subsets. Given that pDCs are in favor of tolerogenic function, our data support that smoking could induce the production of pDCs to manifest immunosuppressive properties in the chronic smokers.