CD8A and neoplasm: On 1 hand, HLA class I molecules are directly involved in the processing and presentation of endogenous antigens (viral antigens, intracellular bacterial antigens, tumor antigens, etc.)by antigen-presenting cells (APCs); on the other hand, when CD8+ cytotoxic T lymphocytes specifically recognize antigenic peptides presented by APCs, HLA class I molecules bound to antigenic peptides must be recognized at the same time to be activated, and then, adaptive immune responses can be initiated.