Fig 1: The up-regulation of PD-L1 in anti-PD-1 treated mice is mediated by IFN?. (A) C57BL/6 mice were subcutaneously injected with 1 × 106 SM1 murine melanoma tumor cells. Mice were treated with 15 mg/kg anti-PD-1 or a vehicle control for 21 days. Tumor nodules were isolated to evaluate the expression of IFN? by qRT-PCR (B), and PD-L1, PD-L2, B7-H3, B7-H4, OX40L, and GAPDH by immunoblot (C). SM1 melanoma cells were treated in vitro with NextA or vehicle and then co-cultured with CD3/CD28 activated splenocytes in the presence or absence of IFN? blocking antibody at 1:1000 and 1:100 dilutions. Then, the expression of PD-L1 was analyzed by qRT-PCR (D), and the expression of IFN? by ELISA (E).