SR1 HSPC–derived CD34⁺ and CD34⁻ cells that express CD7 engraft neonatal immunodeficient mice. (A) SR1-expanded HSPCs or naive HSPCs were differentiated on OP9-DL1 for 14 days, and CD34⁺CD7⁺ and CD34⁻CD7⁺ cells were sorted by flow cytometry. Neonatal NSG mice were injected intrahepatically with 1.0 × 10⁶ cells of either subset (n = 3-4 mice per group). (B) Thymuses were harvested after 4 weeks, and cells were flow cytometrically analyzed for CD45, CD4, and CD8 expression. The percentage of live CD45⁺ cells and CD4 and CD8 are shown for mice transplanted with either subset. (C) Thymus cellularity for transplanted mice. *P < .05, representing statistical significance as determined by 2-way analysis of variance. DAPI, 4′,6-diamidino-2-phenylindole.