CD8 (Cluster of Differentiation 8) is a cell surface glycoprotein found on most cytotoxic T lymphocytes that mediate efficient cell-cell interactions within the immune system. The CD8 antigen acts as a co-receptor with the T-cell receptor on the T lymphocyte to recognize antigens displayed by an antigen presenting cell (APC) in the context of class I MHC molecules. CD8 is found on a T cell subset of normal cytotoxic/suppressor cells which make up approximately 20-35 % of human peripheral blood lymphocytes. The CD8 antigen is also detected on natural killer (NK) cells, subpopulations of peripheral blood null cells, thymocytes and bone marrow cells. The CD8 co-receptor functions as either a homodimer composed of two alpha chains, or as a disulfide-linked heterodimer composed of one alpha and one beta chain. Both alpha and beta chains share significant homology to immunoglobulin variable light chains. The majority of CD8+ T cells express CD8 as a alpha/beta heterodimer. In HIV, the HIV-2 envelope glycoprotein binds CD8 alpha chain (but not the beta chain).
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Protein Aliases: CD8; CD8 antigen, alpha polypeptide (p32); CD8 antigen, beta polypeptide 1 (p37); CD8a; CD8alpha; CD8b; CD8beta; Leu-2; Leu2 T-lymphocyte antigen; MAL; OKT8 T-cell antigen; T cell co-receptor; T lymphocyte surface glycoprotein beta chain; T-cell antigen Leu2; T-cell surface glycoprotein CD8 alpha chain; T-cell surface glycoprotein CD8 beta chain; T-lymphocyte differentiation antigen T8/Leu-2; T8 T-cell antigen
Gene Aliases: CD8; CD8A; CD8B; CD8B1; LEU2; LY3; LYT3; MAL; p32; P37