Viability of B- and T-ALL populations after PTL exposure. (A) Low minimal residual disease risk (MRD; n = 12) and (B) high MRD risk (n = 8) B-ALL subpopulations were sorted using antibodies against CD34 and CD19. (C) Six patients were sorted using antibodies against CD133 and CD19. Squares represent the low-risk patients; triangles, intermediate risk; and circles, high-risk. (D) Subpopulations from 9 T-ALL patients were sorted using antibodies against CD34 and CD7. Two of the 9 patients were low MRD risk and are depicted with open squares. High MRD risk patients are depicted with filled circles. Graphs show the proportion of viable B- and T-ALL subpopulations after exposure to 10μM PTL. Data are expressed as a percentage of untreated controls. Each symbol represents results from individual patients. Horizontal bars represent mean viability. **P ≤ .01; ***P ≤ .001.