CD274 and melanoma: indicated that exosomes in malignant melanoma also express PD-L1, which can directly bind to PD-1 on the surface of T cells and inhibit T cell function, and can also bind to PD-L1 monoclonal antibody.PD-L1 monoclonal antibodies may be neutralized by exosomes PD-L1 before they have a role to play (55).