Donor-derived MR-DCs injected systemically are presented for a short-time by host CD11c^hi DCs. (A) Different subsets of splenic APCs from B6 mice nontreated (control) or injected 20 hours earlier with BALB/c MR-DCs were isolated by FACS sorting, then γ-irradiated and used as stimulators of CFSE-labeled 1H3.1 CD4⁺ T cells in 5-day MLCs. CFSE-labeled 1H3.1 T cells cultured alone or stimulated with splenic CD11c⁺ CD8⁻ DCs prepulsed with IEα_52-68 were included as negative and positive controls, respectively. Dilution of CFSE in 1H3.1 T cells (gated on CD4⁺ cells) was analyzed by flow cytometry. Numbers are percentages of dividing 1H3.1 CD4⁺ T cells. (B) Assessment of duration of presentation by host (B6) splenic APCs of the BALB/c IEα_52-68 allopeptide derived from reprocessing of BALB/c MR-DCs on various days, before adoptive transfer of CFSE-labeled 1H3.1 CD4⁺ T cells. Numbers are percentages of dividing 1H3.1 CD4⁺ T cells in vivo. (A-B) Representative results from 2 or more independent experiments are shown.