CpG-activated but not immature pDCs are able to recall CD8⁺T-cell memory. (A-B) The 129sv mice were injected with cDCs loaded or not with OVA_257-264 peptide (1st injection) and hemisplenectomized 7 days later. The frequency of OVA-specific IFN-γ–producing cells in the spleen was determined by ELISPOT assay (A). Six weeks after the first injection, these mice were boosted with a second injection of cDCs, immature pDCs, or CpG-activated pDCs, loaded or not with OVA_257-264 peptide (2nd injection). (B) The frequency of OVA-specific IFN-γ–producing cells after the boost was determined by ELISPOT. Each bar corresponds to an individual mouse. Error bars represent SDs. Results are representative of 3 independent experiments. (C) CTL responses in mice that have received peptide-loaded pDCs (□) or CpG-activated pDCs (▪) 6 weeks after being primed with OVA-loaded cDCs. Primary CTL responses induced by cDCs are shown in the inset. Each curve corresponds to one mouse. Results are representative of 2 independent experiments.