Aged splenic cDCs have impaired ability to cross-prime naïve CD8⁺ T cells <i>in vitro</i>.

<p>Total (A-D) or CD8α⁺ (E) cDCs purified from young and old mice were incubated with 1 mg/mL OVA mixed with 20 μg/mL polyU/DO for 90 minutes. Additional cDCs from young and old mice were incubated with RPMI or OVA as control. cDCs were then washed and cultured for 3 days with CFSE-labeled CD8β⁺ T cells isolated from the spleen of OT-I mice at different DC:T cell ratios. After culture, T cell proliferation and CD25 expression were analyzed by flow cytometry. (A) Representative histograms of T cell proliferation are shown from 1:1 ratio. (B, E) Percentages of proliferating T cells, (C) CD25 expression and (D) IFN-γ content in culture supernatants, determined by ELISA. Data show the mean ± SEM. *p < 0.05, **p < 0.01. Results are representative of 3 independent experiments (3–4 mice/age group/experiment).