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).
CD8; CD8a; Leu-2; Lyt-2.1 lymphocyte differentiation antigen (AA at 100); MAL; T-cell surface glycoprotein CD8 alpha chain; T-cell surface glycoprotein Lyt-2