PDCs induce IL-10 in CD4⁺CD25⁻ T cells and expand T cells expressing intermediate levels of FoxP3. CD4⁺ T cells were separated into CD25⁺ and CD25⁻ fractions, combined with PDCs, and compared with regard to SEB-induced cytokine production at 36 hours. (A) IL-10 and IFN-γ were measured with the cytokine secretion assay. One of 2 similar experiments is shown. (B) IL-10 was measured in the supernatants with CBA, and the relative contribution of IL-10 from each subset is shown. Two separate experiments are indicated by distinct symbols. (C) PDCs or CD11c⁺ DCs were cocultured with autologous CFSE-labeled CD4⁺ T cells in the presence of HCMV (MOI of 5), and intracellular expression of FoxP3 was measured on day 6.5. The upper 2 plots are gated on CD3⁺ cells. The lower plots are gated on T cells that have not proliferated (CFSE^high), being CD25⁻ (green) or CD25⁺ (blue), or on cells that have proliferated (CFSE^low; red). One representative experiment of 3 is shown.