Impact of type-I-interferon on monocyte subsets and their differentiation to dendritic cells. An in vivo and ex vivo study in multiple sclerosis patients treated with interferon-beta.

In addition to CD14++ "classical" monocytes, human peripheral blood contains CD14+CD16+ "pro-inflammatory" monocytes, which may be influenced by IFNb treatment. By fluorescence activated cell sorting (FACS) analysis, 94 multiple sclerosis (MS) patients revealed normal absolute and relative numbers of both monocyte populations (71 untreated, 23 IFNb-treated). In IFNb-treated patients, CD14+CD16+ monocytes consistently expressed higher CD14, confirmed in 16 patients analyzed longitudinally. Ex vivo, CD1a+CD14+ dendritic cells (DC) were efficiently differentiated from peripheral blood cells from controls and untreated patients, but at considerably reduced efficiency in IFNb-treated patients. Addition of IFNb to the medium further reduced the induction of CD1a+CD14+ cells.IFNb induces a novel immunophenotypic shift in pro-inflammatory monocytes, which appears to be related to reduced formation of dendritic cell precursors.