title: Inhibition of transplant rejection following treatment with anti-B7-2 and anti-B7-1 antibodies.
abstract: Antigen-specific T cell activation depends initially on the interaction of the T cell receptor (TCR) with peptide/MHC. In addition, a costimulatory signal, mediated by distinct cell surface accessory molecules, is required for complete T cell activation leading to lymphokine production and proliferation. CD28 has been implicated as the major receptor on T cells responsible for delivering the costimulatory signal. Although two distinct ligands for CD28, B7-1 and B7-2, have been identified on antigen-presenting cells (APC), the co-stimulatory role of each molecule during a physiological immune response remains unresolved. In the present study, the relative roles of B7-1 and B7-2 interactions were evaluated in an allogeneic pancreatic islet transplant setting. In isolation, anti-B7-2 mAbs and, to a much lesser degree, anti-B7-1 mAbs suppressed T cell proliferative responses to allogeneic islets or splenic APC in vitro. Maximal inhibition of the allogeneic response was observed using a combination of the anti-B7-1 and anti-B7-2 mAbs. Administration of anti-B7-2 but not anti-B7-1 mAbs prolonged C3H allograft survival in B6 recipients, with a combination of both mAbs significantly prolonging rejection beyond either mAb alone. The immunosuppressive effects of the in vivo mAb treatment were not manifested in in vitro analyses as T cells isolated from suppressed mice responded normally to allogeneic stimuli in terms of both proliferation and lymphokine production. However, combined mAb therapy in vivo selectively delayed CD4+ T lymphocyte infiltration into the graft. These data suggest that both B7-1 and B7-2 costimulatory molecules are active in vivo, although B7-2 plays a clearly dominant role in this allograft model. The mechanism of immune suppression in vivo remains unresolved but may occur at sites distinct from the allograft.
mesh_terms: D000069594:Abatacept; D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D015703:Antigens, CD / Q000276:immunology / Q000502:physiology*; D000943:Antigens, Differentiation / Q000502:physiology; D018122:B7-1 Antigen / Q000276:immunology / Q000502:physiology*; D051940:B7-2 Antigen; D060908:CTLA-4 Antigen; D006084:Graft Rejection / Q000517:prevention & control*; D018796:Immunoconjugates; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; 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; D018796:Immunoconjugates; D008562:Membrane Glycoproteins; D000069594:Abatacept