Enhanced Frequencies of CD14++CD16+, but Not CD14+CD16+, Peripheral Blood Monocytes in Severe Asthmatic Patients

CD16+ monocytes are expanded in various inflammatory conditions. Recently it was reported that CD16+ monocytes can be divided into two subsets with contrasting potential of modulating inflammatory responses, namely CD14++CD16+ and CD14+CD16+ monocytes. Here, we characterized and quantified CD14++CD16+ and CD14+CD16+ monocyte subsets in asthmatic patients in the context of severity of disease and different treatment options. Subjects included seventeen severe asthmatics and eighteen moderate asthmatics treated with moderate-to-high doses of inhaled glucocorticosteroids (GCS), twenty nine steroid-naive mild asthmatics and fifteen healthy controls. First, we demonstrated that CD14++CD16+ monocytes, in contrast to CD14+CD16+ monocytes, present significantly higher expression of anti-inflammatory molecule CD163. The frequency of CD14++CD16+, but not CD14+CD16+ monocytes, was significantly higher in patients with severe asthma as compared to mild and moderate asthmatics. However, the frequency of both CD16+ monocyte subsets did not correlate directly with exhaled nitric oxide levels. Short-term administration of oral GCS in patients with exacerbations resulted in a preferential decrease of CD14+CD16+ monocytes. Our study indicates that CD14++CD16+ and CD14+CD16+ monocyte subsets in asthmatics are differentially modulated by both the inflammatory process and GCS treatment.