Figure 6.

PD-1 checkpoint blockade enhances immunity by adoptively transferred Vγ2Vδ2 T cells against PC-3 prostate tumors. (a) Schema of treatment protocol used to evaluate the anti-tumor efficacy of Vγ2Vδ2 T cells with PD-1 checkpoint blockade. Human PC-3 prostate cancer cells were injected s.c. into NSG mice on day 0. On day 13, pamidronate (50 μg/kg) was given i.v. with either an anti-PD-1 or an isotype control mAb (200 μg/mouse) injected i.p. On day 14, 1 × 10⁶ purified Vγ2Vδ2 T cells were inoculated i.v. Two days later, mAb injections were repeated. Treatments continued until week 6. Longitudinal and transverse diameters of the tumors were measured weekly. (b) (left panel) Combination of PD-1 checkpoint blockade and adoptive transfer of Vγ2Vδ2 T cells significantly reduces prostate tumor volume in NSG mice compared with adoptive transfer only. Mean PC-3 tumor volume ± SD is shown for 6–8 mice per group treated with either pamidronate alone (open triangles), pamidronate with purified Vγ2Vδ2 T cells (open squares), pamidronate with control mAb (open circles), pamidronate with anti-PD-1 mAb (closed inverted triangles), pamidronate with purified Vγ2Vδ2 T cells and control antibody (closed triangles), or pamidronate with purified Vγ2Vδ2 T cells and anti-PD-1 mAb (closed circles). **p < .01, mean tumor volume of mice treated with anti-PD-1 mAb and adoptive transfer of Vγ2Vδ2 T cells versus adoptive transfer of Vγ2Vδ2 T cells alone using the Mann-Whitney U test. (right panel) Tumor volume at week 7 of individual mice treated with pamidronate and anti-PD-1 mAb (open triangles), pamidronate with purified Vγ2Vδ2 T cells and control mAb (open circles), or pamidronate with purified Vγ2Vδ2 T cells and anti-PD-1 mAb (closed circles). Bars represent mean values. **p < .01, ***p < .001 using the Mann-Whitney U test