Blockage of allogenic T-cell proliferation and T_H1 polarization by CMV-MoDCs is partially because of IL-6 secretion. (A,C) Monocytes were either mock-infected (Med) or infected with CMV (CMV) or supplemented with IL-6 (50 ng/mL), differentiated in the presence of GM-CSF and IL-13 for 5 days and treated (or not) with ultrapure LPS (200 ng/mL) for 24 hours. (B,D) Supernatant from MoDCs (SN-MoDC) or CMV-MoDCs (SN-CMV-MoDC) were added to monocytes before differentiation in the presence (αIL-6; 15 μg/mL) or not (NT) of anti–IL-6 neutralizing Abs or isotypic Ab as control (iso; 15 μg/mL). (A-B) IL-12 was quantified by CBA on day 6 of culture. (C-D) DCs derived from monocytes as described above were cocultured with naive allogenic T cells for 8 days after adding IL-2 (50 U/mL) on day 5. Cells were fixed, permeabilized, double-labeled with anti–IL-4 and anti–IFN-γ Abs, and analyzed by flow cytometry. (E) Monocytes were either mock-infected (Med), or infected with CMV (CMV), or treated with supernatant (SN) as indicated before differentiation. Naive allogenic T cells were stained with CFSE and cocultured for 5 days with monocyte-derived DCs as indicated. The proliferation of T cells was analyzed by flow cytometry. Error bars represent SD. Representative of ≥ 3 independent experiments. P values were obtained with Student t test.