Treatment of HCC-bearing mice with ICI alone (days 21–34) induced detectable changes in the landscape of CD8+ T cell populations, with a particularly significant further proportional increase in the ‘Exhausted CD8 T Cells’ (Cluster 17) population which is characterized by activation/inhibitory markers (TIM-3, TIGIT, LAG-3, CD39, and PD-1) (Fig. 3E). Here, PDCD1 is linked to hepatocellular carcinoma.