CD8 [C8/468+144B]

The CD8 antigen is a cell surface glycoprotein found on most cytotoxic T lymphocytes that serves as a coreceptor for TCR recognition of MHC class I associated peptides and supports CTL activation by binding to the MHC, while making no direct contact with the peptide.CD8 is expressed on cytotoxic suppressor T cells. It is expressed as a disulphide-linked α/β heterdimer or as an α/α homodimer on T cell subset, thymocytes and NK cells. In normal human tonsil, large numbers of CD8+ lymphocytes were present within the paracortex; occasionally positive cells were also identified within germinal centers and within the investing squamous epithelium. In other tissues, only lymphoid cells and cells of histiocyte lineage showed positive staining for CD8. CD8 alpha chains bind to class I MHC molecules alpha-3 domains. Defects in CD8A are a cause of familial CD8 deficiency (CD8 deficiency). Familial CD8 deficiency is a novel autosomal recessive immunologic defect characterized by absence of CD8+ cells, leading to recurrent bacterial infections.