Phenotype of leukemias generated by HSCs, CLPs, and pro-B cells. Each cell population was transduced with BCR-ABL/GFP and transplanted into preconditioned Rag1^−/− mice. Recipients were killed when they appeared moribund. Single-cell suspensions of bone marrow and spleen cells were prepared and examined for the expression of donor-derived GFP⁺ cells in combination with B-lineage cell-surface antigens. The left panel for each tissue shows the frequency of GFP⁺ cells in that tissue (□) and the proportion of these GFP⁺ cells that expressed CD45R(B220) (■). The right panel for each tissue shows the distribution of cells with a pro-B (▨) and pre-B-cell () phenotype among the GFP⁺ CD45R(B220)⁺ cells. Phenotypic analysis was performed as shown in supplemental Figure 1. Total average number of BCR-ABL/GFP⁺ cells in the bone marrow of mice that received transduced HSCs, CLPs, and pro-B cells was 12.8 (± 4.8) × 10⁶, 17.6 (± 5.7) × 10⁶, and 17.3 (± 9.5) × 10⁶, respectively. Total average number of BCR-ABL/GFP⁺ cells in the spleen of mice that received transduced HSCs, CLPs, and pro-B cells was 116.4 (± 51.1) × 10⁶, 35.2 (± 22.8) × 10⁶, and 44.0 (± 29.7) × 10⁶, respectively.