T-cell proliferation and CD19⁺B-cell clearance. (A) PBMC response to treatment from a representative healthy donor. Cells from healthy donors were cultured for 5 days alone or with 10 nM blinatumomab with or without 500 nM imatinib, 50 nM nilotinib, 5 nM dasatinib, or 25 nM ponatinib. Cells were then assessed by multiparametric flow cytometry gated on CD45⁺ cells. (i) Histograms of CD3⁺ cells assessed for retention of CellTrace Violet. Loss of intensity is a marker of cell proliferation. (ii) CD19⁺ expression and CD3⁺ expression from these samples. Percentage of CD19⁺ cells is shown in the upper left quadrant of each histogram. (B) Combined results of T-cell proliferation from 5 healthy donor samples. Percent of T-cell proliferation was quantified by measuring the percent of T cells diluting CellTrace Violet. Comparisons were performed by Student t test (**P < .01). Each shape represents an individual healthy donor. (C) PBMCs from a representative newly diagnosed patient with Ph⁺ ALL. The sample was incubated for 5 days in the presence of drugs as described above and assessed for T-cell proliferation by CellTrace Violet retention and expression of CD19 and CD3. (D) Response of PBMCs from a patient with relapsed Ph⁺ ALL with a T315I mutation. (E) Combined percent T-cell proliferation from 5 Ph⁺ ALL samples (3 primary Ph⁺ ALL and 2 relapsed Ph⁺ ALL T315I). Each column was compared by Student t test (****P < .0001). Each shape represents an individual patient sample.