Hybrid DCs are effective APCs. B6actOVA mice were irradiated and reconstituted with BALB/c BM. As controls, B6 and BALB/c mice underwent syngeneic transplants. Mice were killed on day 7 and K^b+K^d+ CD11c⁺ cells were sorted (A) along with CD11c⁺ cells from control actOVA and BALB/c mice (not shown). DCs were cultured with CFSE-labeled OT-1 cells at the DC/OT-1 ratios shown. Cultures were harvested at days 3, 4, and 5. Shown is proliferation on day 3 of culture (B); similar data were obtained after 4 and 5 days of culture (not shown). Data are representative of 2 experiments with similar results.