PDCD1 and experimental autoimmune encephalomyelitis: Blocking PD-1/PD-L1 pathway by a monoclonal antibody directed to PD-1 exacerbated the development of autoimmune disease in murine model, such as experimental autoimmune encephalomyelitis (EAE) (35) and diabetes (36), demonstrating that PD-1/PD-L1 pathway regulated autoimmunity by limiting the expansion and activation of autoreactive CD8+ T cells (37).