Cooperative antileukemic effects of anti-CD3 mAbs and chemotherapy. (A) Leukemia burden in blood of NSG mice injected with 10⁶ cells from T-ALL UPNT-420 or UPNT-760. At high tumor burden (day 15 for UPNT-420; day 16 for UPNT-760), mice were treated for 5 consecutive days with either 4 μg per day of control hIgG1 (n = 4), (red) hOKT3γ1[Ala/Ala] (n = 4) (green), or vincristine (0.5 mg/kg) plus dexamethasone (15 mg/kg) (purple) or cotreated with hOKT3γ1[Ala/Ala] (4 µg per day) and vincristine (0.5 mg/kg) plus dexamethasone (15 mg/kg) (orange). (B) Flow cytometric analysis at day 35 of leukemia burden in mice injected with UPNT-760 T-ALL cells and treated as described in panel A. One representative mouse of each group is shown. (C) Leukemia burden in NSG mice injected with 10⁶ cells from T-ALL UPNT-420. At day 15, mice were treated for 5 consecutive days with either 4 μg per day of control mIgG2a (n = 4) (red), OKT3 (n = 4) (blue), or vincristine (0.5 mg/kg) plus dexamethasone (15 mg/kg) (purple) or cotreated with OKT3 (4 µg per day) and vincristine (0.5 mg/kg) plus dexamethasone (15 mg/kg) (orange). (D) Kaplan-Meier survival curves of NSG mice receiving a transplant of T-ALL UPNT-420 and treated as in panel C. **P < .01.