Objective: To study the effects of the active metabolite of vitamin D 3 , 1,25(OH) 2 D 3 , an immunomodulatory hormone, on the generation of so-called immature dendritic cells (iDCs) generated from monocytes (Mo-iDCs). Design and methods: Human peripheral blood monocytes were cultured to iDCs in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 for 1 week, with or without the extra addition of 10 28 M 1,25(OH) 2 D 3 to the culture. Their phenotypes (CD14, CD1a, CD83, HLA-DR, CD80, CD86 and CD40 expression) were examined by¯uorescence-activated cell sorting, and their T-cell stimulatory potential was investigated in allogeneic mixed lymphocyte reaction (allo-MLR). Additionally, their in vitro production of IL-10, IL-12 and transforming growth factor b (TGF-b) were examined by using the enzyme-linked immunosorbent assay. Results: When 1,25(OH) 2 D 3 was added to monocytes in culture with GM-CSF and IL-4, it hampered the maturation of Mo-iDCs. First, the phenotype of the 1,25(OH) 2 D 3 -differentiated DCs was affected, there being impaired downregulation of the monocytic marker CD14 and impaired upregulation of the markers CD1a, CD83, HLA-DR, CD80 and CD40. CD86 was expressed on more 1,25(OH) 2 D 3 -differentiated DCs. Secondly, the T-cell stimulatory capability of 1,25(OH) 2 D 3 -differentiated DCs was upregulated relative to the original monocytes to a lesser degree than DCs differentiated without 1,25(OH) 2 D 3 when tested in an allo-MLR. With regard to the production of cytokines, Staphylococcus aureus cowan 1 strain (SAC)-induced IL-10 production, although not enhanced, remained high in 1,25(OH) 2 D 3 -differentiated DCs, but was strongly downregulated in DCs generated in the absence of 1,25(OH) 2 D 3 . SAC/interferon-g-induced IL-12 production was clearly upregulated in both types of DC relative to those of the original monocytes, and TGF-b production was downregulated. Conclusion: Our data con®rm earlier reports showing that 1,25(OH) 2 D 3 hampers the maturation of fully active immunostimulatory major histocompatibility complex (MHC) class II+, CD1a+, CD80+ DCs from monocytes. Our data supplement the data from other reports by showing that the expression of CD86 was upregulated in 1,25(OH) 2 D 3 -differentiated DCs, whilst the capacity for IL-10 production remained high. Collectively, these data are in line with earlier descriptions of suppressive activities of this steroid-like hormone with respect to the stimulation of cell-mediated immunity.

Background: Dehydroepiandrosterone (DHEA) has been suggested as an immunostimulating steroid hormone, of which the effects on the development of dendritic cells (DC) are unknown. The effects of DHEA often oppose those of the other adrenal glucocorticoid, cortisol. Glucocorticoids (GC) are known to suppress the immune response at different levels and have recently been shown to modulate the development of DC, thereby influencing the initiation of the immune response. Variations in the duration of exposure to, and doses of, GC (particularly dexamethasone (DEX)) however, have resulted in conflicting effects on DC development. Aim: In this study, we describe the effects of a continuous high level of exposure to the adrenal steroid DHEA (10 26 M) on the generation of immature DC from monocytes, as well as the effects of the opposing steroid DEX on this development. Results: The continuous presence of DHEA (10 26 M) in GM-CSF/IL-4-induced monocyte-derived DC cultures resulted in immature DC with a morphology and functional capabilities similar to those of typical immature DC (T cell stimulation, IL-12/IL-10 production), but with a slightly altered phenotype of increased CD80 and decreased CD43 expression (markers of maturity).The continuous presence of DEX at a concentration of 10 26 M in the monocyte/DC cultures resulted in the generation of plastic-adherent macrophage-like cells in place of typical immature DC, with increased CD14 expression, but decreased expression of the typical DC markers CD1a, CD40 and CD80. These cells were strongly reactive to acid phosphatase, but equally capable of stimulating T cell proliferation as immature DC. The production of IL-12 by these macrophage-like cells was virtually shut down, whereas the production of IL-10 was significantly higher than that of control immature DC. Conclusion:The continuous presence of a high level of GC during the generation of immature DC from monocytes can modulate this development away from DC towards a macrophage-like cell. The combination of a low CD80 expression and a shutdown of IL-12 production suggests the possibility of DEX-generated cells initiating a Th2-biased response. These effects by DEX on DC development contrast with those by DHEA, which resulted in a more typical DC although possessing a phenotype possibly indicating a more mature state of the cell.

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