Immunophenotypic analysis of OP9-DL1 cocultures generated from CD34⁺lin⁻CD7⁻, CD34⁺lin⁻CD7^intCD10⁺, and CD34⁺lin⁻CD7^hi cells. Approximately 1500 cells from each population were isolated by FACS and cocultured with OP9/DL1 stroma and TPO, IL-7, and FL. Cells in culture were analyzed (A) by FACS at 2 to 4 weeks for expression of T-lineage markers (CD4, CD8) and CD7 and (B) by RT-PCR for pTα expression. Shown are data from one representative experiment of a total of 7 independent experiments for FACS analysis, and 2 independent experiments for RT-PCR, using different thymus samples.