Dll4^hiDCs induce effector CD4⁺ T-cell differentiation. Dll4^hiDCs or GM-DCs were generated from BM of BALB/c mice. (A-D) CD4⁺ T_Ns were purified from B6 mice, labeled with CFSE, and incubated with BALB/c Dll4^hiDC at escalating DC/T-cell ratios. Five days later, T cells were collected to measure their proliferation (A) and recovery (B). In panel C, dot plots and graphs show the percentages of IFN-γ–producing and IL-17–producing cells among proliferating CD4⁺ T cells that expressed CFSE^low (mean ± SD of triplicates). (D) Graph shows in vitro cytotoxic activity of B6 CD4⁺ T_Ns or BALB/c Dll4^hiDCs activated B6 CD4⁺ T cells (DC/T-cell ratio of 1:4) against A20 leukemia cells. Representative data from 2 independent experiments are shown. (E-G) CFSE-labeled B6 CD4⁺ T_Ns were incubated with BALB/c Dll4^hiDCs or GM-DCs with DC/T-cell ratio of 1:4. Five days later, T cells were collected to measure their proliferation (E) and recovery (F). (G) Dot plots and graphs show the percentages of IFN-γ, IL-17, and tumor necrosis factor α (TNF-α)–producing cells among proliferating CD4⁺ T cells that expressed CFSE^low (mean ± SD of triplicates). (H) B6 Dll4^hiDCs were cultured with CD4⁺ T cells specific to OT-II peptide (OVA_232-239), which were isolated from TCR transgenic OT-II mice in the presence of OT-II peptides (top). BALB/c Dll4^hiDCs were cultured with CD4⁺ T cells isolated from WT B6 mice (bottom). Dot plots and graphs show the percentages of IFN-γ and IL-17 in the different neutralizing Ab condition (mean ± SD of triplicates). *P < .05; **P < .01; ***P < .001.