title: Induction of factor VIII-specific unresponsiveness by intrathymic factor VIII injection in murine hemophilia A.
abstract: BACKGROUND
  Hemophilia A is a congenital bleeding disorder caused by a deficiency of coagulation factor VIII. Approximately 30% of hemophilia A patients develop inhibitors against FVIII following replacement therapy. We have reported that neonatal exposure of FVIII antigen can induce antigen-specific immune tolerance by interferon-gamma (IFN-gamma)-dependent T-cell anergy in hemophilia A mice.
  
  
  OBJECTIVE
  The thymus plays crucial roles in self-tolerance, with negative selection of self-reactive effector T cells and positive selection of self-reactive regulatory T cells. We investigated the possibility of the induction of antigen-specific immune tolerance by intrathymic injection of FVIII in hemophilia A mice.
  
  
  METHODS
  Hemophilia A mice were injected with recombinant FVIII into the thymus under real-time high-resolution image guidance.
  
  
  RESULTS
  Anti-FVIII inhibitory antibody titers in mice challenged with intravenous administration of FVIII were significantly lower in mice (n = 22) that had received thymic FVIII injection than in mice (n = 18) without thymic injection (9.4 +/- 2.3 vs. 122.5 +/- 27.6 BU mL(-1), respectively, P = 0.00078). The CD4(+) T cells from thymic-injected mice could not proliferate or produce interleukin (IL)-2, IL-12 and IFN-gamma in response to FVIII. The CD4(+)CD25(+) T cells generated from thymic-treated mice but not from naïve mice efficiently suppressed the in vitro proliferative response of CD4(+) T cells and blocked the in vivo development of anti-FVIII antibodies in the adoptive transfer.
  
  
  CONCLUSIONS
  These data suggest that intrathymic administration of FVIII could result in immune tolerance by induction of FVIII-specific regulatory T cells.
authors.affiliation: Research Division of Cell and Molecular Medicine, Centre for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan. madochan@jichi.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Madoiwa
authors.forename: T
authors.initials: T
authors.lastname: Yamauchi
authors.forename: E
authors.initials: E
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Hakamata
authors.forename: M
authors.initials: M
authors.lastname: Dokai
authors.forename: N
authors.initials: N
authors.lastname: Makino
authors.forename: Y
authors.initials: Y
authors.lastname: Kashiwakura
authors.forename: A
authors.initials: A
authors.lastname: Ishiwata
authors.forename: T
authors.initials: T
authors.lastname: Ohmori
authors.forename: J
authors.initials: J
authors.lastname: Mimuro
authors.forename: Y
authors.initials: Y
authors.lastname: Sakata
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000096:biosynthesis / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D049109:Cell Proliferation; D005169:Factor VIII / Q000008:administration & dosage / Q000276:immunology*; D005434:Flow Cytometry; D006467:Hemophilia A / Q000276:immunology*; D051379:Mice; D013950:Thymus Gland / Q000378:metabolism*
chemical_list: D001323:Autoantibodies; D005169:Factor VIII