No prolonged survival was observed in response to checkpoint blockade in mice that received IFNγ-stimulated B16 melanoma cells compared with the mice inoculated with unstimulated B16 melanoma cells, suggesting that the improved survival of the EV-treated groups was not due to the presence of MHC class I on the melanoma cells at the time of anti–PD-1/anti–PD-L1 injection (Supplementary Fig. S7C and S7D). Here, PDCD1 is linked to melanoma.