title: Critical influence of natural regulatory CD25+ T cells on the fate of allografts in the absence of immunosuppression.
abstract: BACKGROUND
  Allografts are occasionally accepted in the absence of immunosuppression. Because naturally occurring CD4(+)CD25(+) regulatory T cells (natural CD25(+) Treg cells) have been shown to inhibit allograft rejection, we investigated their influence on the outcome of allografts in nonimmunosuppressed mouse recipients.
  
  
  METHODS
  We compared survival times of male CBA/Ca skin grafts in female CBA/Ca recipients expressing a transgenic anti-HY T-cell receptor on a RAG-1(+/+) (A1[M]RAG+) or a RAG-1(-/-) (A1[M]RAG-) background. Depletion of natural CD25(+) Treg cells in A1[M]RAG+ mice was achieved by in vivo administration of the PC61 monoclonal antibody. The influence of natural CD25(+) Treg cells on the fate of major histocompatibility complex class II-mismatched (C57BL/6X bm12)F1 skin or bm12 heart transplants in C57BL/6 recipients was also assessed. Finally, we investigated the impact of natural CD25(+) Treg cells on the production of T-helper (Th)1 and Th2 cytokines in mixed lymphocyte cultures between C57BL/6 CD4(+) CD25(-) T cells as responders and bm12 or (C57BL/6X bm12)F1 antigen-presenting cells as stimulators.
  
  
  RESULTS
  Male allografts were spontaneously accepted by female A1(M)RAG+ mice but readily rejected by female A1(M)RAG+ mice depleted of natural CD25(+) Treg cells by pretreatment with the PC61 monoclonal antibody. Depletion of CD25(+) Treg cells also enhanced eosinophil-determined rejection of (C57BL/6X bm12)F1 skin grafts or bm12 cardiac grafts in C57BL/6 recipients. Finally, natural CD25(+) Treg cells inhibited the production of interleukin (IL)-2, interferon-gamma, IL-5, and IL-13 in mixed lymphocyte culture in a dose-dependent manner.
  
  
  CONCLUSIONS
  Natural CD25(+) Treg cells control Th1- and Th2-type allohelper T-cell responses and thereby influence the fate of allografts in nonimmunosuppressed recipients.
authors.affiliation: Institute for Medical Immunology, Université Libre de Bruxelles, 8, rue Adrienne Bolland, B-6041 Charleroi (Gosselies), Belgium.
authors.forename: Fleur Samantha
authors.initials: FS
authors.lastname: Benghiat
authors.forename: Luis
authors.initials: L
authors.lastname: Graca
authors.forename: Michel Y
authors.initials: MY
authors.lastname: Braun
authors.forename: Sophie
authors.initials: S
authors.lastname: Detienne
authors.forename: Fabrice
authors.initials: F
authors.lastname: Moore
authors.forename: Sofia
authors.initials: S
authors.lastname: Buonocore
authors.forename: Véronique
authors.initials: V
authors.lastname: Flamand
authors.forename: Herman
authors.initials: H
authors.lastname: Waldmann
authors.forename: Michel
authors.initials: M
authors.lastname: Goldman
authors.forename: Alain
authors.initials: A
authors.lastname: Le Moine
mesh_terms: D000818:Animals; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D005260:Female; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology / Q000473:pathology; D007165:Immunosuppression Therapy; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000276:immunology* / Q000378:metabolism; D016038:Skin Transplantation / Q000276:immunology / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism; D014180:Transplantation; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D016207:Cytokines; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2