title: B7-1 or B7-2 is required to produce the lymphoproliferative phenotype in mice lacking cytotoxic T lymphocyte-associated antigen 4 (CTLA-4).
abstract: The costimulatory molecules B7-1 and B7-2 regulate T lymphocyte activation by delivering activating signals through CD28 and inhibitory signals through cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). The importance of CTLA-4-mediated inhibition was demonstrated by the uncontrolled T cell activation and lymphoproliferative disease that develops in CTLA-4-deficient (-/-) mice. To examine the role of B7 signaling in the activation of CTLA-4-deficient T cells, we bred CTLA-4(-/-) mice with mice lacking B7-1, B7-2, or both B7 molecules. The CTLA-4/B7-1(-/-) and the CTLA-4/B7-2(-/-) mice develop lymphoproliferation and enhanced T cell activation. Mice lacking CTLA-4, B7-1, and B7-2 have a normal life-span, and do not have lymphocytic infiltrates in any organs, or increased T cell activation. Therefore, the two B7 molecules have overlapping functions, since either B7-1 or B7-2 alone can cause the CTLA-4(-/-) phenotype. Elimination of both B7-1 and B7-2 from the CTLA-4- deficient mouse abrogates the lymphocyte activation and disease, and does not reveal evidence for additional stimulatory CD28 ligands. The CTLA-4(-/-) phenotype can be reproduced with anti-CD28 antibody in mice lacking CTLA-4, B7-1, and B7-2, but wild-type mice are unaffected by the same treatment. This suggests that the inhibitory function of CTLA-4 can overcome strong CD28-mediated signaling in vivo.
authors.affiliation: Immunology Research Division, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.damandelbr@bics.bwh.harvard.edu
authors.forename: D A
authors.initials: DA
authors.lastname: Mandelbrot
authors.forename: A J
authors.initials: AJ
authors.lastname: McAdam
authors.forename: A H
authors.initials: AH
authors.lastname: Sharpe
mesh_terms: D000069594:Abatacept; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology*; D051940:B7-2 Antigen; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D060908:CTLA-4 Antigen; D002455:Cell Division / Q000276:immunology; D004195:Disease Models, Animal; D005434:Flow Cytometry; D018796:Immunoconjugates; D008232:Lymphoproliferative Disorders / Q000276:immunology; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D000906:Antibodies; D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018106:CD28 Antigens; D017252:CD3 Complex; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D008562:Membrane Glycoproteins; D000069594:Abatacept