title: Distinct tolerance pathways in sensitized allograft recipients after selective blockade of activation signal 1 or signal 2.
abstract: BACKGROUND
  CD4-targeted therapy or blocking of CD28-B7 T-cell costimulation may produce indefinite cardiac allograft survival in presensitized rats. This study analyzes the immune events associated with tolerance pathways after the blockade of activation signal 1 (CD4 monoclonal antibody [mAb]) or signal 2 (CTLA4Ig).
  
  
  RESULTS
  Lewis rats sensitized with Brown Norway skin grafts reject LBNF1 cardiac allografts in <36 hr. Animals were treated with RIB-5/2, a nondepleting CD4 mAb, or with CTLA4Ig + LBNF1 spleen cells. RIB-5/2 monotherapy uniformly produced permanent cardiac graft acceptance, whereas CTLA4Ig produced indefinite graft survival in about 50% of sensitized rats. Spleen cells (100 x 10(6)) from CD4 mAb-treated rats conferred donor-specific tolerance after transfer into new sets of recipients. This tolerant state could be then transferred with regulatory cells in an infectious manner into new cohorts of engrafted rats. In contrast, features of infectious tolerance could be detected in CTLA4Ig-treated hosts after infusion of >300 x 10(6) of splenocytes. CD4 mAb therapy abolished the transcription of both T helper (Th)1 and Th2 cytokines compared with rejecting controls. In contrast, CTLA4Ig treatment resulted in a selective sparing of Th2-type cytokines. Surviving grafts in both groups were largely protected from signs of chronic rejection.
  
  
  CONCLUSIONS
  CD4 mAb-induced blockage of activation signal 1 or CTLA4Ig-mediated blockage of costimulatory signal 2 may induce a true transplantation tolerance in sensitized rats, as documented by permanent graft acceptance and attenuation of chronic injury. The infectious pathway operates in a cell dose-dependent manner. Th2-type deviation in the graft itself is not required for tolerance maintenance, and it does not necessarily lead to chronic injury.
authors.affiliation: Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: K
authors.initials: K
authors.lastname: Onodera
authors.forename: A
authors.initials: A
authors.lastname: Chandraker
authors.forename: H D
authors.initials: HD
authors.lastname: Volk
authors.forename: T
authors.initials: T
authors.lastname: Ritter
authors.forename: M
authors.initials: M
authors.lastname: Lehmann
authors.forename: H
authors.initials: H
authors.lastname: Kato
authors.forename: M H
authors.initials: MH
authors.lastname: Sayegh
authors.forename: J W
authors.initials: JW
authors.lastname: Kupiec-Weglinski
mesh_terms: D000069594:Abatacept; D000818:Animals; D019138:Antibodies, Blocking / Q000502:physiology; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000627:therapeutic use; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000502:physiology / Q000627:therapeutic use; D001161:Arteriosclerosis / Q000517:prevention & control; D015704:CD4 Antigens / Q000276:immunology*; D060908:CTLA-4 Antigen; D016207:Cytokines / Q000502:physiology; D004306:Dose-Response Relationship, Immunologic; D006085:Graft Survival / Q000276:immunology; D016027:Heart Transplantation / Q000276:immunology*; D007108:Immune Tolerance / Q000187:drug effects / Q000276:immunology / Q000502:physiology; D018796:Immunoconjugates; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D018418:Th2 Cells / Q000502:physiology; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D015704:CD4 Antigens; D060908:CTLA-4 Antigen; D016207:Cytokines; D018796:Immunoconjugates; D007166:Immunosuppressive Agents; C108171:RIB 5-2 monoclonal antibody; D000069594:Abatacept