Flow cytometric analysis of engraftment and differentiation of in vitro–derived CD34⁺CD7⁺⁺CD5⁻(proT1)- and CD34⁺CD7⁺⁺CD5⁺(proT2)-cells in immunodeficient mice. (A) Human UCB CD34⁺CD38^−/lo cells were differentiated on OP9-DL1 cells for 10 days and CD34⁺CD7⁺⁺ CD5⁻ (proT1)- and CD34⁺ CD7⁺⁺ CD5⁺ (proT2)-cells were sorted by flow cytometry. (B) Neonatal NSG mice were injected intrahepatically with 2.0 × 10⁵ cells of either subset (n ≥ 8 mice/group). Thymuses were harvested after 4 weeks and stained for CD45, CD4, CD8, and CD3. The percentage of human CD45⁺ cells present in the thymus of NSG mice transplanted with proT1-cells (average thymus cellularity 27.6 × 10⁴ ± 6.6 × 10⁴) or proT2 cells (average thymus cellularity 31.6 × 10⁴ ± 4.0 × 10⁴) are shown. CD4, CD8, and CD3 cell surface expressions are shown on CD45⁺-gated thymocytes. The results shown are representative of at least 3 independent experiments. SSC, side scatter.