Induction of factor VIII-specific unresponsiveness by intrathymic factor VIII injection in murine hemophilia A.
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.
Madoiwa
S
S
Research Division of Cell and Molecular Medicine, Centre for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan. madochan@jichi.ac.jp
Yamauchi
T
T
Kobayashi
E
E
Hakamata
Y
Y
Dokai
M
M
Makino
N
N
Kashiwakura
Y
Y
Ishiwata
A
A
Ohmori
T
T
Mimuro
J
J
Sakata
Y
Y
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*
D001323:Autoantibodies; D005169:Factor VIII