CD25−CD4+ T cells were cultured essentially as described in Figure 6. Cultured cells were incubated with CFSE-labeled naïve CD25−CD62Lhigh CD4+ responder T cells at a ratio of 1:1 in the presence of CD90-depleted APCs and anti-CD3 for 3 d. Proliferation of naïve responder cells was evaluated according to CFSE dilution. Histograms show CFSE staining of responder T cells cultured alone (positive) or cocultures with ex vivo isolated CD25+CD4+ Tregs (ex vivo), with T cells cultured for 6 d under neutral conditions (neutral), with T cells cultured for 6 d in the presence of TGF-β (TGF-β), with T cells cultured for 6 d under neutral conditions and restimulated under neutral conditions (neutral/neutral), and with T cells cultured for 6 d in the presence of TGF-β followed by restimulation under neutral conditions (TGF-β/neutral). Representative data from one out of three independent experiments with similar results are depicted. (72 KB PDF)