T-cell IFN-γ is required for Dll4^hiDCs programming to reduce CD4⁺ T-cell–mediated GVHD. Unstimulated WT or Ifng^−/− CD4⁺ T_Ns (0.5 × 10⁶) and allogeneic Dll4^hiDC-induced WT or Ifng^−/−CD4⁺ T cells (0.5 × 10⁶) of B6 background were separately transplanted with TCD-BM (5.0 × 10⁶) into lethally irradiated BALB/c mice. Survival (A) and GVHD clinical score (B) of the recipients were monitored over time. Data shown here are pooled from 2 independent experiments. (C) Six days after transplantation, donor T cells were isolated from the spleens and livers. Graphs show the numbers of donor CD4⁺ T cells in recipient BALB/c mice (mean ± SD). (D) Graph shows the percentage of annexin V⁺ cells among donor CD4⁺ T cells. (E) Plots and graphs show the percentages of donor CD4⁺ T cells producing IFN-γ, IL-17, and TNF-α in the spleen and the liver. (F) Histograms show the expression of indicated chemokine receptors on the surface of unstimulated WT or Ifng^−/− CD4⁺ T_Ns and Dll4^hiDC-stimulated WT or Ifng^−/− CD4⁺ T cells 7 days after in vivo transfer. Representative results of 2 independent experiments are shown. *P < .05; **P < .01; ***P < .001.