In addition, the harsh conditions of the tumor microenvironment make it difficult for TAA-specific CD8+ T cells to infiltrate the tumor, and they can be suppressed directly by the ligation of co-inhibitory receptors expressed on activated CD8+ T cells with their ligands on tumor cells or indirectly by suppressor cells such as T regulatory cells and myeloid-derived suppressor cells. The gene discussed is CD8A; the disease is neoplasm.