In vivo propagating ability of PTL-treated ALL subpopulations. (A) Unsorted and sorted ALL cells were treated with PTL for 20-24 hours in vitro, and then injected into NSG mice. Cells were inoculated at the following doses per mouse: unsorted (1-5 × 10⁶), CD34⁺/CD19⁺ (8 × 10⁴-1 × 10⁶), CD34⁺/CD19⁻ (1.8 × 10³-1.2 × 10⁵), CD34⁻ (1.5-2 × 10⁶ B-ALL), CD34⁺/CD7⁺ (1-1.5 × 10⁶), CD34⁺/CD7⁻ (4-6 × 10⁴), and CD34⁻ (1.5-5 × 10⁶ T-ALL). After 4-12 weeks, leukemia cell engraftment in BM was analyzed by flow cytometry using a panel of antibodies. (B-C) Levels of engraftment attained using unsorted and sorted subpopulations from 5 B-ALL patients (B) and from 5 T-ALL patients (C). Each symbol depicts the engraftment level of human leukemia cells from the patients indicated as measured in the BM of individual mice. Closed symbols represent mice inoculated with untreated cells; opens symbols, mice inoculated with PTL-treated cells. Solid horizontal bars represent mean engraftment levels using untreated cells; dashed bars represent mean engraftment levels using PTL-treated cells.