Figure 4.

In vitro tumor cell-killing by day 14 γδT cells. (A) Myeloid leukemia KBM7 target cells were labeled with the cell membrane dye PKH26 and mixed with day 14 γδT cells at target to effector cell ratios as indicated. After 6 h of incubation at 37°C, remaining live target cells were determined by including flow cytometry counting beads. Percent (%) killing refers to the ratio of remaining to input target cells × 100. As control (Ctrl), targets cells were cultured for 6 h in the absence of γδT cells; representative of three experiments. (B) KBM7 target cells were cultured overnight in the presence (+HMBPP) or absence (−) of 1 μM HMBPP. The two cultures were labeled with either PKH26 or Cellvue and added to day 14 γδT cells at a target to effector cell ratio of 1:10. To examine the mechanisms of target cell-killing, antibodies to γδTCR (anti-Vγ9; 10 μg/ml and anti-Vδ2; 1/100 dilution) and isotype antibody (mouse IgG1; 10 μg/ml) were included in the cultures. After 6 h of culture, percent killing was determined as outlined above by gating on PKH26⁺ (HMBPP-treated KBM7) and CellVue⁺ (control KBM7) cells; representative of two experiments.