Figure 1.

Mechanisms of exosomal PD-L1 mediated immunosuppression. In general, the interaction between exosomal PD-L1 and PD-1 on T cells directly causes immunosuppression. In addition, exosomal PD-L1 up-regulates the expression of PD-L1 in myeloid cells through the NF-κB pathway, makes them transform into myeloid immune cells, and indirectly inhibits the activation and proliferation of T cells. Besides, exosomal PD-L1 can be blocked by anti-PD-L1 mAbs, which may result in a low response rate to anti-PD-L1 mAb treatment. The end point of these mechanisms is T cell inactivation and tumor progression.