Phenotype and T-cell priming abilities of IFN-λ–treated DCs. iDCs were left untreated or were treated with IFN-β, IFN-λ, or LPS for 24 hours. (A) Surface expression of MHC class I, MHC class II, CD80, CD86, CD40, and CD83 were accessed by flow cytometry. IFN- or LPS-treated cells (black lines) were compared with iDCs (gray lines) and isotopic control conditions (filled areas). Histograms are representative of results obtained with cells from 18 blood donors. (B) DCs were tested for their ability to stimulate allogeneic CD4⁺ T-cell proliferation in vitro. MLR culture assays were performed at least in quadruplicate with various DC/T ratios. Similar results were obtained in 6 independent experiments.