Dendritic cells generated in the presence of interferon-alpha stimulate allogeneic CD4+ T-cell proliferation: modulation by autocrine IL-10, enhanced T-cell apoptosis and T regulatory type 1 cells.

Dendritic cells (DCs) generated in the presence of IFN-alpha (IFN-DCs) exhibit high expression of major histocompatibility and co-stimulatory molecules and a potent ability to stimulate CD8(+) T-cell responses. Here, we found that IFN-DCs were more potent stimulators of bulk and purified CD8(+) T-cell proliferation, as compared with IL-4-DCs. In contrast, IFN-DCs were less efficient than IL-4-DCs in stimulating allogeneic CD4(+) T-cell proliferation, due to a weak induction of naive CD4(+)CD45RO(-) T-cell proliferation by these DCs. However, both DC populations induced similar levels of proliferation of memory CD4(+)CD45RO(+) T cells. IFN-DCs and IL-4-DCs exhibited a similar phenotype and production of IL-10 following maturation induced by CD40 ligation. In contrast, IFN-DCs produced higher levels of IL-10 during the first days of differentiation. In addition, neutralization of IL-10 during the differentiation of DCs increased the expression of DC-LAMP and MHC class II by IFN-DCs, and the ability of IFN-DCs to stimulate allogeneic CD4(+) T-cell proliferation at similar levels, than IL-4-DCs. Independently of IL-10 production, IFN-DCs were found to induce higher levels of CD4(+)T-cell apoptosis, this effect being more sticking on naive T cells. Finally, we demonstrated that IFN-DCs induced a differentiation bias of naive CD4(+) T cells towards Th1 and Tr1 cells, compared to IL-4-DCs. Taken together, these results indicate that, despite the induction of Tr1 cells and enhanced apoptosis of naive CD4(+) T cells, IFN-DCs are potent stimulators of CD8(+) and memory CD4(+) T cells, and induce a strong polarization of naive CD4(+) T cells towards Th1 cells, further supporting their use in immune-based therapy.