Tolerogenic functions of IFN-λ–treated DCs are IL-2 dependent. iDCs or IFN-β, IFN-λ, or LPS-treated DCs were used for stimulating allogeneic CD4⁺ T-cell proliferation in vitro at a 1:10 DC/T-cell ratio. Neutralizing anti–IL-2 or control IgG was added to the cultures as indicated. (A) CD4⁺ T-cell proliferation was determined by [³H]-thymidine incorporation after 8 days of culture under stimulating iDC or λDC conditions. (B) Quantification of Foxp3 mRNA expression by real-time PCR in MLR cultures of DCs and CD4⁺ T cells as indicated. Experiments were performed on a pool of T cells from 3 blood donors. Results are expressed relative to GAPDH level.