CD8

Also called T cell suppressor/cytotoxic cells, OKT8

Cell surface glycoprotein, member of immunoglobulin superfamily; at 2p12

Heterodimer of an alpha and a beta chain linked by two disulfide bonds; heterodimer on thymocytes and homodimer on peripheral blood T cells

MHC class I restricted receptor; binds to nonpolymorphic region of class I molecules; may increase avidity of interactions between cytotoxic T cell and target cell during antigen-specific activation

Can kill target cells by recognizing peptide-MHC complexes on them or by secreting cytokines capable of signaling through death receptors on target cell surface

CD8 alpha cells promote survival and differentiation of activated T cells into memory CD8+ T cells, which may become clonal (but not malignant) in the elderly (Immunol Rev 2005;205:170)

Contribute to initiation, progression and regulation of autoimmune responses (Curr Opin Immunol 2005;17:624)

Associated with lymphoepithelioma-like carcinoma of lung (AJSP 2002;26:715); low CD8:CD3 ratio in epidermotrophic component of lymphoid infiltrate is suggestive of mycosis fungoides (Mod Path 2003;16:857)

Uses: cytotoxic T cell marker

Drawings: (1) CD8+ T cell interaction with antigen presenting cell #1; #2; (3) destruction of viral infected cell

Micro images: (4) infiltrating lymphocytes in lymphoepithelioma-like carcinoma of cervix-figure 3; (5) T cell lymphoma (type not specified); (6) sinus lining cells in splenic hamartomas #1 are CD8+; #2 (figure 3A); (8) nodal cytotoxic T cell lymphoma; (9) mycosis fungoides; (10) intraepithelial lymphocytes in duodenum (figure 1c); (11) increased intraepithelial lymphocytes at villous tip (figure 2e)

Positive staining (normal): cortical thymocytes (70-80%), T cells (25-35% of mature peripheral T cells, mostly cytotoxic T cells); NK cells (30%, which are also CD3 negative)

Positive staining (disease): epidermotrophic lymphocytes in mycosis fungoides (AJSP 2002;26:450), subcutaneous panniculitis-like T cell lymphoma, indolent T cell lymphoblastic proliferation, sinus lining cells in splenic hemartoma, heterotopic ovarian splenoma, NK/T cell lymphoma (variable), some post-thymic T cell lymphomas, rarely mantle cell lymphoma (AJCP 1998;109:689), rarely CLL (AJCP 1994;102:212, Archives 2000;124:1361), T cell infiltrate in 30% of cases of nodular regenerative hyperplasia of liver (Hum Path 2004;35:1241)

Negative stains: adult T cell leukemia/lymphoma, littoral cell hemangioma of spleen

References: Mod Path 2002;15:1131; OMIM 186910 (alpha chain), OMIM 186730 (beta chain)