title: Cutting edge: MHC class I triggering by a novel cell surface ligand costimulates proliferation of activated human T cells.
abstract: BY55 is a human cell surface molecule whose expression is restricted to NK cells, a subset of circulating CD8+ T lymphocytes, and all intestinal intraepithelial T lymphocytes. Here, we report that BY55 is a novel NK receptor showing broad specificity for both classical and nonclassical MHC class I molecules, and that optimal binding requires a prior aggregation of MHC class I complexes. Using BY55 transfectants, we have identified functional consequences of MHC class I/ligand interactions for the class I-bearing cell. The triggering of MHC class I molecules on human T cell clones by BY55 delivered a potent proliferative signal in the presence of soluble CD3 mAb. The costimulatory signal provided by MHC class I ligation was only seen in activated, and not resting, peripheral blood T cells. This observation represents an additional and/or alternative pathway to CD28 costimulation and may be of particular relevance in memory T cells lacking CD28, such as intestinal intraepithelial T lymphocytes, which are CD28- but BY55+.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U448, Henri Mondor Hospital, Faculté de Medecine, Créteil, France.
authors.forename: S
authors.initials: S
authors.lastname: Agrawal
authors.forename: J
authors.initials: J
authors.lastname: Marquet
authors.forename: G J
authors.initials: GJ
authors.lastname: Freeman
authors.forename: A
authors.initials: A
authors.lastname: Tawab
authors.forename: P L
authors.initials: PL
authors.lastname: Bouteiller
authors.forename: P
authors.initials: P
authors.lastname: Roth
authors.forename: W
authors.initials: W
authors.lastname: Bolton
authors.forename: G
authors.initials: G
authors.lastname: Ogg
authors.forename: L
authors.initials: L
authors.lastname: Boumsell
authors.forename: A
authors.initials: A
authors.lastname: Bensussan
mesh_terms: D000818:Animals; D015703:Antigens, CD; D018106:CD28 Antigens / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D058851:GPI-Linked Proteins; D015789:HLA-A2 Antigen / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011971:Receptors, Immunologic / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D012995:Solubility; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D014162:Transfection