DL1 and Jag1 support T-cell development from thymic progenitor cells in vitro. (A) CD34⁺CD1a^- thymic precursor cells were cocultured with OP9-DL1 or OP9-Jag1 for 4 weeks. Cells were analyzed for expression of CD4 and CD8 every week. (B) Analysis after 4 weeks for expression of TCRαβ, TCRγδ, and CD3 (CD3, filled histogram; isotype control, gray line). One representative experiment of 3 is shown.