CD8A and neoplasm: For instance, multiple tumors ultimately lose the expression of key proteins involved in antigen presentation, such as beta-2-microgoblulin (B2M), hence becoming virtually invisible to CD8+ cytotoxic T lymphocytes197 or express increased amounts of immunosuppressive molecules, such as CD274 (best known as PD-L1), thus actively suppressing T cell activation in the tumor microenvironment (TME)198.