Effect of donor-derived MR-DC administration on the indirect CD4⁺ T-cell response. Host B6 mice received CFSE-labeled 1H3.1 Thy1.1⁺ CD4⁺ T cells and were injected intravenously (or not) the next day with control syngeneic (B6) MR-DCs, or BALB/c MR-DCs alone or plus agonistic CD40 Ab (intraperitoneally), the latter used as a positive control to promote full 1H3.1 T-cell activation. (A) Dot plots show proliferation, surface phenotype, and percentages of apoptotic cell death of splenic 1H3.1 CD4⁺ T cells (gated on Thy1.1 cells) analyzed by FACS, 3 days after MR-DC administration. (B) Absolute numbers of 1H3.1 Thy1.1⁺ CD4⁺ T cells in the spleen, 3 and 14 days after B6 (control) or BALB/c MR-DC (with and without CD40 Ab, intraperitoneally) intravenous administration in host B6 mice, in the absence or presence of BALB/c cardiac allografts transplanted 7 days after MR-DC administration. Absolute numbers of 1H3.1 cells did not change significantly in lymph nodes (cervical, axilar, mesenteric, inguinal), assessed 3 days after MR-DC infusion. (C) Amounts of IFN-γ (by ELISA) secreted by splenocytes of each group of recipient B6 mice restimulated ex vivo (24 hours) with the BALB/c IEα_52-68 allopeptide. (D) Percentages and absolute numbers of splenic 1H3.1 FoxP3⁺ CD4⁺ T cells 14 days after MR-DC injection in each group of recipient B6 mice. NS indicates not significant. (A-D) Results represent 2 independent experiments with 3 or more animals per group (mean ± SD).