Acquisition of IFN-λ responsiveness by monocytes during DC differentiation. (A) Quantification of IFN-LR1 mRNA expression in monocytes, monocyte-derived DCs, and freshly purified blood DCs (i) or in IFN-β DCs and macrophages (ii). Top and bottom panels represent experiments on 2 different blood donors. (B) Kinetics of IFN-LR1 mRNA expression by monocytes during their differentiation into DCs in the presence of GM-CSF and IL-4. (C) Quantification of 2′5′ oligo adenylate synthetase mRNA expression by monocytes and DCs from the same blood donors after 4 hours of IFN-β or IFN-λ treatment. Transcript levels were quantified by real time RT-PCR relative to GAPDH. (D) Monocytes were cultured for 4 days in the presence of GM-CSF alone or were supplemented with IFN-β, IFN-λ, or IL-4. Expression of the surface markers CD11c and CD14 were accessed by flow cytometry. For all experiments, similar results were obtained with cells from 2 to 3 blood donors.