PDCD1LG2 and melanoma: To further validate the role of PD‐L2 on the membrane of melanoma cells‐derived EVs, we used the B16‐F10 melanoma cell line, which express endogenous PD‐L1 and PD‐L2, to establish stable PD‐L2 knockout (shPDL2) and PD‐L1 knockout (shPDL1) cell lines (Figure S3c).