Figure 3. Preexisting TIL is insufficient for the effects of PD-L1 blockade.

(A) B6.Rag^–/– mice (n = 5) were inoculated with 1 × 10⁶ MC38 cells. After tumors were established, mice were treated with 200 μg anti–PD-L1 on days 8 and 11. Tumor growth was measured twice a week. (B) C57BL/6 mice (n = 5) were inoculated with 1 × 10⁶ MC38 cells. Mice were treated with 200 μg anti–PD-L1 on days 8 and 11. For CD8⁺ T cell depletion, mice were treated with 200 μg anti-CD8 on days 8, 11, and 14. (C–E) MC38 tumor–bearing mice (n = 5 per group) were treated with 200 μg IgG or anti–PD-L1 on days 8 and 11. Mice were also treated with control (C) or FTY720 from day 0 (D) or day 8 (E). (F) MC38 tumor-bearing mice were treated with IgG or anti–PD-L1 (n = 3 per group). Two days later, dLN were isolated and single-cell suspensions were prepared. Cells were cocultured with or without MC38 cells for 2 days. IFN-γ⁺ cells were measured by ELISPOT. (G) MC38 tumor–bearing mice were treated with anti–PD-L1 and FTY720 as in C–E. Three days after anti–PD-L1 treatment, dLNs were isolated. ELISPOT assay was performed. Data indicate mean ± SEM and are representative of 2 independent experiments. Statistical analysis was performed using an unpaired Student’s 2-tailed t test. *P < 0.05; **P < 0.01; ***P < 0.001. ND, not detectable.