Fig. 2
From: Hypoxia-inducible factors: master regulators of hypoxic tumor immune escape
Proposed mechanism underlying tumor immune escape. Tumor immune escape is related to antigenic deletion, tumor cell leakage, lack of costimulatory signals on the tumor cell surface, and the antiapoptotic effects of tumor cells. Tumor cells bind to PD-1 on tumor-infiltrating lymphocytes via PD-L1 that mediates immune escape in the tumor microenvironment. Tumor cells also inhibit immune cells by releasing exosomes rich in surface PD-L1 to escape from immune system recognition