FIGURE 1.

The immunosuppressive activity of programmed death‐ligand 1 (PD‐L1) in tumor microenvironment (TME). Dendritic cells (DCs) express PD‐L1 to suppress responses from CD8⁺ T cells. PD‐L1⁺ tumor cells and PD‐L1⁺ myeloid‐derived suppressor cells (MDSCs) suppress CD8⁺ T cell effector function and promote their exhaustion. PD‐L1 expression is also related to the macrophage polarization toward the pro‐tumor macrophage type 2 (M2) phenotype. This preferential polarity is stimulated by PD‐L1⁺ regulatory T cells (Tregs). PD‐L1 acts via interaction with a programmed death‐1 receptor (PD‐1). High expression of this receptor in a PD‐L1^high TME stimulates Treg proliferation and promotes CD8⁺ T cell apoptosis