Selective depletion of CD14+ CD16+ monocytes by glucocorticoid therapy

Glucocorticoids (GC) are potent anti-inflammatory and immunosuppressive agents that act on many cells of the body, including monocytes. Here we show that a 5-day course of high dose GC therapy differentially affected the CD14⁺⁺ and the CD14⁺ CD16⁺ monocyte subpopulations in 10 patients treated for multiple sclerosis. While the classical (CD14⁺⁺) monocytes exhibited a substantial increase from 495 ± 132 to 755 ± 337 cells/μl, the CD14⁺ CD16⁺ monocytes responded with a pronounced decrease from 36 ± 15 to 2 ± 3 cells/μl (P < 0.001). In 4/10 patients the CD14⁺ CD16⁺ monocytes fell below detection limits (< 0.2 cells/μl). This observation was confirmed when the CD14⁺ CD16⁺ monocytes were identified by virtue of their low CD33 expression as these cells decreased as well. After discontinuation of GC therapy the CD14⁺ CD16⁺ monocytes reappeared and reached normal levels after 1 week. The profound depletion of CD14⁺ CD16⁺ monocytes by GC as described here is a novel effect of GC action in vivo and may contribute to GC-mediated immunosuppression. Determination of the number of this monocyte subset may also serve to monitor the effectiveness of GC therapy in patients requiring immunosuppressive treatment.