International Immunology, Vol 10, 1637-1646, Copyright © 1998 by Oxford University Press
ND Jones, NC Fluck, AL Mellor, PJ Morris and KJ Wood
Intrathymic (i.t.) injection of donor alloantigens has proved to be an
effective strategy for the induction of tolerance. However, the mechanisms
by which tolerance is induced and maintained after transplantation remain
unclear. In this report we show that tolerance to donor cardiac allografts
can be induced across a MHC class I difference by i.t. injection of donor
splenocytes and transient T cell depletion. Furthermore, using
H-2K(b)-specific TCR transgenic mice (BM3), we demonstrate that prolonged
deletion of donor-reactive thymocytes was essential to induce tolerance by
i.t. injection and this was dependent upon donor cells persisting in the
thymus. Examination of the kinetics of thymic export following i.t.
injection revealed that prolonged deletion of thymocytes was required to
delay export of new T cells to the periphery until the time of
transplantation. Importantly, after transplantation donor cell persistence
in the thymus and i.t. deletion were no longer necessary to maintain
tolerance. The graft itself or cells from the graft was responsible for
maintaining tolerance at this stage. These findings reveal that multiple
mechanisms are responsible for the induction and maintenance phases of
tolerance to alloantigens in vivo after i.t. delivery, and that a complex
inter- relationship between donor cell persistence in the thymus, i.t.
deletion, thymic export of T cells and the timing of transplantation is
involved.
ARTICLES
The induction of transplantation tolerance by intrathymic (i.t.) delivery of alloantigen: a critical relationship between i.t. deletion, thymic export of new T cells and the timing of transplantation [In Process Citation]
Nuffield Department of Surgery, University of Oxford, John Radcliffe Hospital, Headington, UK.
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