Circulating human plasmacytoid dendritic cells are highly sensitive to corticosteroid administration

Plasmacytoid dendritic cells (pDC), the major interferon-producing cell type found in Hum. blood, have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Previous Studs. in SLE have shown substantial deviations from Norm. in this minor but immunologically important leukocyte population. Many of the lupus patients studied were Rec. corticosteroids. To determine the effects of steroid Admin. on pDC in healthy adults, four volunteers were given prednisone, 15-30 mg daily, for 4 days. Both counts of pDC,/their ability to produce IFN-α were significantly reduced (P = 0.02/0.004, respectively) during steroid administration,/rapidly recovered after discontinuation of the hormones. The overall reduction in pDC-derived IFN appeared to be attributable to falls of both No. of circulating cells/of IFN produced per pDC. The effects observed with pDC were comparable in magnitude but opposite in Dir. to that observed for granulocytes. In contrast, other blood leukocytes were little affected during steroid therapy.