AbstractBackgroundMyeloid dendritic cells type 2 (mDC2s) are a new subtype of DCs identified in both the circulation and the lung and suggested to have a role in allergic asthma.MethodsCirculating mDC2s were enumerated in 19 healthy, 18 atopic nonasthmatic, 18 mild atopic asthmatic, and 16 moderate/severe atopic asthmatic subjects using flow cytometry.ResultsThe number of circulating mDC2s was significantly lower in atopic subjects compared with healthy controls and in asthmatic subjects compared with nonasthmatic subjects. There was a trend toward lower levels of circulating mDC2s with increasing allergy and asthma severity. The largest differences were seen in moderate/severe atopic asthmatics being 430.78 ± 48.91/ml compared with healthy controls being 767.05 ± 101.64/ml (P < 0.05).ConclusionsCirculating mDC2s are lower in atopic and asthmatic subjects, which suggests that these cells efflux from the blood into the airways in patients with allergic disease.