title: Spleen plays an important role in maintaining tolerance after removal of the vascularized heart graft.
abstract: BACKGROUND
  This study addresses the question of the mechanism for maintaining tolerance to donor alloantigen in the absence of antigen and the role of secondary lymphoid tissues.
  
  
  METHODS
  Depleting anti-CD4 antibody administration in conjunction with allogeneic heart transplantation generates donor-specific operational tolerance. Primary C57BL/6 heart grafts were transplanted into the neck cavity of the anti-CD4 antibody pretreated C3H/He mice. At day 50, functioning heart grafts were removed from tolerant mice. At day 100, a secondary C57BL/6 or a third-party heart was transplanted into the abdomen.
  
  
  RESULTS
  Anti-CD4 antibody therapy induced CD4CD25 regulatory T cells by 50 days after transplantation, as depleting anti-CD25 treatment in tolerant mice abrogated graft prolongation when spleen leukocytes were adoptively transferred to syngeneic mice. Tolerance was maintained by CD4CD25 regulatory T cells via a CTLA-4 signal at 100 days, even after removal of the primary graft at day 50. Administration of anti-CD25 antibody immediately after removal of the primary graft did not break tolerance, as five out of six second allografts transplanted at day 100 were accepted. Anti-CD25 antibody therapy in conjunction with splenectomy, but not thymectomy, immediately after removal of primary heart grafts at day 50 broke tolerance at day 100; all allografts were rejected.
  
  
  CONCLUSIONS
  The spleen is important in maintaining CD4CD25 regulatory T cells after primary allograft removal.
authors.affiliation: Department of Surgery II, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Chosa
authors.forename: Masaki
authors.initials: M
authors.lastname: Hara
authors.forename: Akira
authors.initials: A
authors.lastname: Watanabe
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Matsuzaki
authors.forename: Kunihide
authors.initials: K
authors.lastname: Nakamura
authors.forename: Kimikazu
authors.initials: K
authors.lastname: Hamano
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Wood
authors.forename: Toshio
authors.initials: T
authors.lastname: Onitsuka
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology; D000943:Antigens, Differentiation / Q000276:immunology; D060908:CTLA-4 Antigen; D006348:Cardiac Surgical Procedures; D004334:Drug Administration Schedule; D016027:Heart Transplantation / Q000276:immunology*; D007108:Immune Tolerance / Q000187:drug effects; D053645:Interleukin-2 Receptor alpha Subunit / Q000032:analysis / Q000276:immunology; D007519:Isoantigens / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains; D011184:Postoperative Period; D013154:Spleen / Q000276:immunology*; D013156:Splenectomy; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology; D014019:Tissue Donors; D016042:Transplantation, Heterotopic; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D007519:Isoantigens