PDCD1 and hepatocellular carcinoma: For example, our previous research found that the level of PD-1+, TIGIT+, TIM-3 co-inhibitory molecules of adaptive immune CD4+, CD8+T, NK cells representing the exhaustion function gradually increased during the pathological process of chronic hepatitis B virus to cirrhosis and progressed HBV-HCC (Liu et al., 2019; Yu et al., 2021).