PDCD1 and hepatocellular carcinoma: Significant signaling pathways identified in HCC included HLA-E and CLEC2C. Notably, the interaction between HLA-E expressed by CD28+PD-1+ Tc cells and the corresponding NKG2C receptor on γδ T cells was enhanced in HCC(Supplementary Figure S5A), whereas that between CLEC2C from CD28+PD-1+ Tc cells and KLRB1 on CD4+ T cells was lower in HCC (Supplementary Figure S5B).