PDCD1 and hepatocellular carcinoma: In agreement with previous work, we show that MAIT cells in HCC tumors express higher levels of T cell activation (CD38, HLA-DRA) and exhaustion markers (PDCD1, CTLA4, HAVCR2), but lower levels of the effector function-associated genes CD160 and KLRG1 (Figure 3A) (20).