A role for TGFbeta and B cells in immunologic tolerance after intravenous injection of soluble antigen.
BACKGROUND
Intravenous injection of soluble antigen has been reported to induce immunologic tolerance through a variety of mechanisms including T-cell deletion, anergy, and suppression. To clarify the reported discrepancies, we studied mechanisms of intravenous tolerance to a defined transgenic minor transplantation antigen in mice.


METHODS
Wild-type C57BL/6 (B6) mice or congenic B6 B-cell knockout mice were made tolerant to beta-galactosidase (beta-gal). Clinical tolerance was assessed by placement of B6 beta-gal transgenic (tg) and third-party skin grafts. In vitro analysis of T- and B-cell immunity and in vivo treatment with anti-TGFbeta antibodies were used to define mechanisms of induced tolerance.


RESULTS
Intravenous injection of beta-gal induced true immunologic tolerance to beta-gal tg skin in wild-type but not in B-cell-deficient recipients, suggesting that antigen presentation by B cells was required for the effect. The tolerogenic manipulation primed a population of CD4+, beta-gal-specific, TGFbeta-producing T cells. Although evidence for both anergy and suppression were observed, subsequent data demonstrated that TGFbeta was a critical immunoregulatory mediator of the tolerant state: neutralizing anti-TGFbeta antibodies fully prevented the induction of tolerance to B6 beta-gal tg skin grafts. Second male beta-gal tg grafts placed onto female recipients that were previously made tolerant to female beta-gal tg skin were rapidly rejected, however, suggesting that this TGFbeta-induced tolerance could not be linked to additional antigenic determinants.


CONCLUSIONS
The studies demonstrate a critical role for TGFbeta in mediating tolerance after intravenous injection of antigen but additionally raise concerns about the stability of this tolerant state.
Valujskikh
A
A
Department of Medicine, Case Western Reserve University and The Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Ohio 44106, USA.
VanBuskirk
A M
AM
Orosz
C G
CG
Heeger
P S
PS
D000818:Animals; D000941:Antigens / Q000008:administration & dosage* / Q000276:immunology*; D001402:B-Lymphocytes / Q000502:physiology*; D005260:Female; D006084:Graft Rejection; D007108:Immune Tolerance / Q000502:physiology*; D007156:Immunologic Memory; D007275:Injections, Intravenous; D007937:Leukapheresis / Q000379:methods; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000235:genetics; D008822:Mice, Transgenic / Q000235:genetics; D016038:Skin Transplantation / Q000276:immunology; D012995:Solubility; D016212:Transforming Growth Factor beta / Q000502:physiology*; D001616:beta-Galactosidase / Q000235:genetics / Q000276:immunology
D000941:Antigens; D016212:Transforming Growth Factor beta; D001616:beta-Galactosidase