IL-10 does not regulate T-cell activation by ISS-activated PDCs. (A-B) Purified PDCs (3-5 × 10⁴) were stimulated with ISS (5 μg/mL) in combination with CD40L-transfected L cells for 24 hours. Naive CFSE-labeled allogenic T cells were then added (1:5) and incubated for 3 additional days. (B) Either IL-10 (1 ng/mL) or anti-IL-10R MAb (2.5 μg/mL) was added at the time of T-cell addition. Cells were gated on CD3 and examined for the frequency of dividing cells on the basis of CFSE dilution by flow cytometry. Representative results of 10 donors are shown.