Fig. 7.

4-1BB-dependent suppression of CD4⁺ T cells by IDO-expressing DC subpopulations. SEA-injected C57BL/6 mice were treated with rat IgG or anti-4-1BB mAb on PI Days 0 and 2. DLN cells were prepared from rat IgG- or anti-4-1BB mAb-treated mice on PI Day 10 and then used for the purification of each population including CD11c⁺, PDCA-1⁺, and PDCA-1^– DCs and CD4^–CD11c⁺ and CD8^–CD11c⁺ DCs. Responder CD4⁺ T cells were purified from rat IgG-treated mice on PI Day 10. (A) CD11c⁺, PDCA-1⁺, and PDCA-1^– DCs were cultured with CD4⁺ T cells in the presence or absence of 0.1 μg/ml SEA for 3 days. CD11c⁺, CD4-depleted (ΔCD4) CD11c⁺, and CD8-depleted CD11c⁺ DCs were also mixed with CD4⁺ T cells in coculture (C). Cultured cells were pulsed with [³H]-thymidine (1 μCi/well) during the last 12 h, harvested onto glass fiber filter mats, and analyzed for [³H]-thymidine incorporation by liquid scintillation counting. (B, D). IDO expression in freshly purified DC population on Day 10. Expression level of IDO was confirmed by RT-PCR. The plotted data are means ± sd (*, P<0.05; ***, P<0.001). The results are representative of three independent experiments.