In conclusion, multiple mechanisms may limit the TAA -specific CD8+ T-cell responses in HCC: failure of TAA processing and presentation; insufficient levels of CD4 help; suppression of both CD4+ and CD8+ T cells by Tregs; and negative regulation by PD-1/PD-L1 pathway [61, 62] (Figure 2). This evidence concerns the gene CD4 and hepatocellular carcinoma.