FIGURE 1.

The mechanisms by which tumor ExoPD-L1 induce immunosuppression. (A) ExoPD-L1 originating from tumor cells induces T cell dysfunction in the tumor microenvironment by directly ligating to PD-1 on T cells as well as stationing on PD-L1-negative tumor cells, while its immunoregulatory effect remains intact. ExoPD-L1 also migrates to macrophages and dendritic cells, but the potential effects remain unknown. (B) ExoPD-L1 is able to leave tumor foci and enter the draining lymph node to mediate T cell suppression. (C) ExoPD-L1 can enter and circulate in the blood. (D) ExoPD-L1 inhibits the immune response in spleen and decreases spleen size.