The OP9 cell line expressing the human Notch ligand Jagged1 (OP9-Jag1) supports development of CD34⁺CD1a^–human thymic precursor cells into TCRαβ⁺or TCRγδ⁺T cells and BDCA2⁺CD123^hipDCs. CD34⁺CD1a^– thymic precursors were cultured for up to 24 days on OP9-Jag1 stromal cells and analyzed by flow cytometry for surface expression of CD123, BDCA2, CD1a, CD4, CD8, TCRαβ, and TCRγδ on the days indicated. Numbers represent the percentages of cells that fall within the electronic gate. In the histograms, shaded curves show isotype controls and open curves show specific stainings. CD1a mean fluorescence intensities (MFIs) are 17.4 (day 3), 44.6 (day 5), 90 (day 10), 244 (day 14), 400 (day 19), 411 (day 24). Results are representative of 3 independent experiments. RCN indicates relative cell number.