Cell-cycle analysis. UCB CD34⁺ cells were cultured on either OP9-Del1 (▪) or OP9-C stroma (▦), and after 7 to 14 days cells were stained with BDCA-2 and Hoescht to measure cell cycle by flow cytometry. Results represent the means ± SD values of gated BDCA-2⁺ cells in the different phases of cell cycle obtained from 4 independent experiments. A representative histogram of the cell cycle of BDCA-2⁺ cells cultured onto OP9-Del1 stroma is inserted.