title: Biliary glycoprotein (CD66a), a cell adhesion molecule of the immunoglobulin superfamily, on human lymphocytes: structure, expression and involvement in T cell activation.
abstract: The biliary glycoproteins (BGP or CD66a), a group of different splice variants of a single gene, are members of the carcinoembryonic antigen family and the immunoglobulin superfamily. Recently, we detected CD66a on IL-2 activated lymphocytes. In this study we characterized the structure and the expression pattern of BGP on human lymphocytes and investigated its role in T cell activation. Lymphocytes express 2 of the 13 known splice variants, i.e. BGPa and BGPb, which are glycosylated in a lymphocyte-specific manner. Both BGPa and BGPb have the long cytoplasmic tail, which contains two immunoreceptor tyrosine-based inhibitory motif (ITIM)-like motifs, but differ in their extracellular region containing 4 and 3 immunoglobulin-like domains, respectively. On PBL BGP is expressed in small amounts only on B cells and Th cells. Stimulation with IL-2 leads to a strong up-regulation of BGP by these cells, and induces de novo BGP expression on gammabeta T cells, CD8+ and CD56+ cells, but not on CD16+ lymphocytes. This up-regulation of BGP seems to be part of the physiological process of T cell activation, since stimulation with anti-CD3 mAb is sufficient to induce BGP up-regulation. Based on the presence of the two ITIM-like motifs, one may expect that BGP inhibits T cell activation, but surprisingly, engagement of BGP enhances the proliferation of anti-CD3-stimulated T cells.
authors.affiliation: Institute of Immunobiology, Medical Faculty, University of Freiburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Kammerer
authors.forename: S
authors.initials: S
authors.lastname: Hahn
authors.forename: B B
authors.initials: BB
authors.lastname: Singer
authors.forename: J S
authors.initials: JS
authors.lastname: Luo
authors.forename: S
authors.initials: S
authors.lastname: von Kleist
mesh_terms: D015703:Antigens, CD / Q000032:analysis* / Q000737:chemistry / Q000502:physiology; D000943:Antigens, Differentiation / Q000032:analysis* / Q000737:chemistry / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000032:analysis*; D000939:Epitopes; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008970:Molecular Weight; D009844:Oligosaccharides / Q000032:analysis; D000080506:Sialyl Lewis X Antigen; D013601:T-Lymphocytes / Q000737:chemistry* / Q000276:immunology
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; C069847:CD66 antigens; D015815:Cell Adhesion Molecules; D000939:Epitopes; D009844:Oligosaccharides; D000080506:Sialyl Lewis X Antigen