Cytotoxic CD8+ T cells, CD4+ T cells, and NK cells work together to maintain immune surveillance, whereas abundant immune cells that resident in HCC contribute to immune evasion to prompt tumor progression, such as myeloid-derived suppressor cells (MDSC), regulatory T (Treg) cells, and tumor-associated macrophages (TAMs). The gene discussed is CD8A; the disease is hepatocellular carcinoma.