The CD8α⁺CD4⁻ but not the CD8α⁻CD4⁺ DC subset inhibits up-regulation of IL-13Rα1, prevents apoptosis, and restores neonatal IFN-γ responses. Newborn BALB/c mice were given neonatal DO11.10 T cells without (Nil) or with 10⁵ CD8α⁺CD4⁻ or CD8α⁻CD4⁺ DCs from adult IL-12^+/+ or IL-12^−/− BALB/c mice and were injected 24 h later with 100 μg Ig-OVA. (A) The mice were killed within 2 wk, primary Th1 cells were isolated on the basis of IFN-γ secretion, and IL-13Rα1 expression was evaluated by spot blot. Each bar represents the mean ± SD of duplicate spots. (B–H) 7 wk after exposure to Ig-OVA the mice were challenged with 125 μg OVA peptide in CFA. 10 d later, the splenic cells (10⁶ cells/well) were stimulated for 24 h with 10 μM OVA peptide, and production of IFN-γ was measured by ELISPOT (B) and apoptosis was evaluated by Annexin V staining of KJ1-26⁺/IFN-γ⁺ splenic cells (C–H). For neutralization of endogenous IL-12 where indicated (IL-12^+/+ CD8α⁺CD4⁻/anti–IL-12), the mice were given i.p. 50 μg anti–IL-12 antibody (clone C17.8) on days 1, 2, and 3 after neonatal transfer of DO11.10 T cells and DCs. For stimulation with OVA peptide in the presence of rIL-12 where indicated (IL-12^−/−CD8α⁺CD4⁻ + IL-12), the culture was supplemented with 2 ng/ml rIL-12. Each bar in B represents the mean ± SD of triplicate wells.