title: B7 expression on T cells down-regulates immune responses through CTLA-4 ligation via T-T interactions [corrections].
abstract: Although B7 on APCs has a well-recognized role in T cell costimulation, little is known about the functional significance of constitutive and activation-induced B7 expression that also occurs on T cells. To analyze the role of B7 on T cells, B7-1/B7-2-deficient mice (B7 double knockout) and mice overexpressing B7-2 exclusively on T cells (B7-2 transgenic) were used as T cell donors for allogeneic transplant recipients, and graft-vs-host disease (GVHD) was assessed. B7 double-knockout T cells resulted in significant GVHD acceleration compared with wild-type T cells. Conversely, B7-2 transgenic donor T cells mediated reduced GVHD mortality compared with wild-type T cells. Data indicated that B7 expression on T cells down-regulated alloresponses through CTLA-4 ligation. This study is the first to provide definitive in vivo data illustrating the importance of T cell-associated B7 as a negative regulator of immune responses in a clinically relevant murine model of GVHD. The up-regulation of B7 on T cells may be an important component of normal immune homeostasis.
authors.affiliation: Cancer Center and Department of Pediatrics, Division of Bone Marrow Transplantation, University of Minnesota, 425 East River Road, Minneapolis, MN 55455, USA.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Taylor
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lees
authors.forename: Sylvie
authors.initials: S
authors.lastname: Fournier
authors.forename: James P
authors.initials: JP
authors.lastname: Allison
authors.forename: Arlene H
authors.initials: AH
authors.lastname: Sharpe
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Blazar
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000943:Antigens, Differentiation / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D018122:B7-1 Antigen / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051940:B7-2 Antigen; D016026:Bone Marrow Transplantation / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D060908:CTLA-4 Antigen; D002450:Cell Communication / Q000235:genetics / Q000276:immunology*; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D006086:Graft vs Host Disease / Q000235:genetics / Q000276:immunology / Q000401:mortality / Q000517:prevention & control; D008024:Ligands; D008213:Lymphocyte Activation / Q000235:genetics; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D015375:Receptors, Interleukin-2