Figure 4. mIL-15 induced tumor-specific IFNγ secretion and lytic activity.
On day 21, CT26-bearing mouse splenocytes were harvested and incubated with irradiated CT26 cells at a ratio of 50:1. Cultures were incubated for 4 days. A, 1 × 106 effector cells were cultured with CT26-tumor cells at a ratio of 20:1 for 6 h. Brefeldin A (10 µg/mL) was added to the cultures for the last 5 h. Cells from each group were first stained with APC conjugated anti-CD8, then intracellularly stained with PE-anti-IFNγ. Five hundred thousand events were collected for each sample by a flow cytometer. B; tumor-specific CD8+ T-cell target cell killing activities were detected by a non-radioactive cytotoxicity assay. PBS (open triangles), mIL-15 (open squares), mIL-15 + anti-PD-L1 (filled triangles) and mIL-15 + anti-PD-L1 + anti-CTLA4 (filled diamonds) groups are shown in panel B. The figures are representative of three independent experiments.