Figure 2.

Schematic diagram of the effect of exosomal PD-L1 on tumor microenvironment. At the primary tumor site, T cells interact with PD-L1 positive cells, resulting in immunosuppression, and the types of cytokines released also changed, expanding the impact of immunosuppression. Exosomes carrying PD-L1 cargo are released into the blood and have a similar immunosuppressive effect on premetastatic niche, so that the metastatic tumor can escape the monitoring of the immune system.