title: Tracking the immunoregulatory mechanisms active during allograft tolerance.
abstract: Immunoregulatory mechanisms dependent on regulatory CD4+ T cells are believed to be critical in the maintenance of peripheral tolerance to allografts. However, a detailed characterization of the effects of these regulatory T cells has been hampered by the absence of a simple means to track and study them. In this work we provide evidence that in a murine model of islet transplantation the interactions between alloaggressive and regulatory T cells can be studied in vitro and in vivo at the single-cell level. The observations made in both an in vitro coculture system and an in vivo CFSE-based adoptive transfer model indicate that lymphocytes from tolerant allograft recipients 1) proliferate weakly to donor strain allogeneic cells but vigorously to third-party strain cells; and 2) suppress the proliferation of naive syngeneic CD4+ and CD8+ T cells to donor tissue in a cell dose- and Ag-specific manner. These effects depend on the presence of CD4+CD25+ T cells and are neutralized by anti-CTLA4 mAb or rIL-2. The principal effect of anti-CTLA4 is directed against the naive, not regulatory, T cell population. These results can be replicated in vivo by transferring lymphocyte populations into transplant recipients, proving that the graft-protecting actions of regulatory T cells are blunted by a rise in the number of allodestructive T cells (pool size model) and depend on the presence of CD4+CD25+ T cells and the integrity of the CTLA4/B7 pathway.
authors.affiliation: Department of Medicine, Division of Immunology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sánchez-Fueyo
authors.forename: Martina
authors.initials: M
authors.lastname: Weber
authors.forename: Christoph
authors.initials: C
authors.lastname: Domenig
authors.forename: Terry B
authors.initials: TB
authors.lastname: Strom
authors.forename: Xin Xiao
authors.initials: XX
authors.lastname: Zheng
mesh_terms: D000069594:Abatacept; D019264:Adoptive Transfer; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen; D002478:Cells, Cultured; D006084:Graft Rejection / Q000276:immunology; D018796:Immunoconjugates; D007376:Interleukin-2 / Q000494:pharmacology; D016381:Islets of Langerhans Transplantation / Q000276:immunology; D007519:Isoantigens / Q000276:immunology; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion; D051379:Mice; D008811:Mice, Inbred DBA; D015375:Receptors, Interleukin-2 / Q000276:immunology; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000637:transplantation; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D023001:Transplantation Tolerance / Q000276:immunology*; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D007376:Interleukin-2; D007519:Isoantigens; D015375:Receptors, Interleukin-2; D000069594:Abatacept