Pro-tumor immune cells, including regulatory T cells (Treg), myeloid-derived suppressor cells (MDSCs), and M2-polarized macrophages, can suppress effective immune responses against tumor cells and create an immunosuppressive tumor microenvironment; anti-tumor immune cells, including CD8 T cells, NK cells, DCs, and M1-polarized macrophages, can promote effective anti-tumor immune responses (23). The gene discussed is CD8A; the disease is neoplasm.