title: Active suppression of allogeneic proliferative responses by dendritic cells after induction of long-term allograft survival by CTLA4Ig.
abstract: Costimulatory blockade using cytotoxic T lymphocyte-associated antigen 4 immunoglobulin (CTLA4Ig) efficiently down-regulates immune responses in animal models and is currently used in autoimmune and transplantation clinical trials, but the precise cellular and molecular mechanisms involved remain unclear. Rats that received allogeneic heart transplants and were treated with adenoviruses coding for CTLA4Ig show long-term allograft survival. The immune mechanisms regulating induction of long-term allograft acceptance were analyzed in splenocytes using mixed leukocyte reactions (MLRs). MLRs of splenocytes but not purified T cells from CTLA4Ig-treated rats showed higher than 75% inhibition compared with controls. Splenocytes from CTLA4Ig-treated rats inhibited proliferation of naive and allogeneically primed splenocytes or T cells. MLR suppression was dependent on soluble secreted product(s). Production of soluble inhibitory product(s) was triggered by a donor antigen-specific stimulation and inhibited proliferation in an antigen-nonspecific manner. CTLA4Ig levels in the culture supernatant were undetectable and neither interleukin-10 (IL-10), transforming growth factor beta 1 (TGF beta 1), IL-4, nor IL-13 were responsible for suppression of MLRs. Inhibition of nitric oxide (NO) production or addition of IL-2 could not restore proliferation independently, but the combined treatment synergistically induced proliferation comparable with controls. Stimulation of APCs using tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE) or CD40L and addition of IL-2 normalized MLRs of CTLA4Ig-treated splenocytes. Finally, dendritic cells (DCs), but not T cells, from CTLA4Ig-treated rats inhibited naive MLRs. Altogether, these results provide evidence that after in vivo CTLA4Ig treatment, splenocytes, and in particular DCs, can inhibit alloantigen-induced proliferative responses through secretion of inhibitory products, thus promoting alloantigen-specific tolerance in vivo.
authors.affiliation: Institut national de la santé et de la recherche médicale U 437, Nantes, France.
authors.forename: Cecile
authors.initials: C
authors.lastname: Guillot
authors.forename: Séverine
authors.initials: S
authors.lastname: Ménoret
authors.forename: Carole
authors.initials: C
authors.lastname: Guillonneau
authors.forename: Cécile
authors.initials: C
authors.lastname: Braudeau
authors.forename: Maria G
authors.initials: MG
authors.lastname: Castro
authors.forename: Pedro
authors.initials: P
authors.lastname: Lowenstein
authors.forename: Ignacio
authors.initials: I
authors.lastname: Anegon
mesh_terms: D000069594:Abatacept; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017951:Antigen Presentation; D018106:CD28 Antigens / Q000502:physiology; D023201:CD40 Ligand / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured / Q000276:immunology; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D004357:Drug Synergism; D005822:Genetic Vectors / Q000627:therapeutic use; D006085:Graft Survival; D016027:Heart Transplantation / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology; D018796:Immunoconjugates / Q000235:genetics / Q000627:therapeutic use*; D007165:Immunosuppression Therapy; D007378:Interleukins / Q000494:pharmacology; D007519:Isoantigens / Q000276:immunology; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000502:physiology; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism; D053245:RANK Ligand; D051381:Rats; D011917:Rats, Inbred Lew; D053246:Receptor Activator of Nuclear Factor-kappa B; D011994:Recombinant Proteins / Q000494:pharmacology; D013154:Spleen / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D016042:Transplantation, Heterotopic; D014184:Transplantation, Homologous / Q000276:immunology*
chemical_list: D018106:CD28 Antigens; D002352:Carrier Proteins; D018796:Immunoconjugates; D007378:Interleukins; D007519:Isoantigens; D008222:Lymphokines; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011994:Recombinant Proteins; C508960:TGFB1 protein, human; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D023201:CD40 Ligand; D009569:Nitric Oxide; D000069594:Abatacept