Flow cytometric analysis of the expression of TCR-αβ and TCR-γδ on progenitor T cells arising following coculture of human CB–derived HSCs with OP9-DL1 cells. Human CB–derived HSCs give rise to 3 populations of progenitor T cells that can be discriminated based on the level of expression of CD7 and CD1a. Gated populations of cells CD7⁺CD1a⁺ (gate A), CD7⁺⁺CD1a⁺ (gate B), CD7⁺⁺CD1a^– (gate C) from day 44 cocultures were stained for the expression of TCR-αβ (gated histograms presented in top panel) or TCR-γδ (gated histograms presented in bottom panel). The percentage of gated T progenitor populations of TCR-positive cells is displayed within the histogram.