CD8A (CD8, Leu2, MAL, p32) is a cell surface glycoprotein found on most cytotoxic T lymphocytes that mediates efficient cell-cell interactions within the immune system. It acts as a coreceptor with the T-cell receptor on the T lymphocyte to recognize antigens displayed by an antigen presenting cell in the context of class I MHC molecules. CD8A mutations cause CD8 deficiency, described by frequent bacterial infections. In immunohistochemistry, CD8A has cytoplasmic positivity, and it is used to mark normal and malignant T cells, cytotoxic and suppressor T cells, cortical thymocytes, NK cells, and dendritic cells. In cancer, CD8A is used to classify lymphomas and identify CD8-positive melanomas. CD8A also distinguishes splenic hamartoma (positive) from hemangioma and littoral cell angioma (negative). References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; J Clin Invest 2001;108:117, PMID: 11435463; PLoS One 2010;5:e8437, PMID: 20052413;