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Mechanisms of Transplantation Tolerance

Mechanisms of Transplantation Tolerance Transplantation tolerance, the long-term acceptance of grafted tissue in the absence of continuous immunosuppression, remains an elusive goal in humans, but it has been achieved in animal models using numerous approaches. The mechanisms behind graft acceptance vary according to the means used to create the state of acceptance. Several major mechanisms can now be recognized. While thymic deletion of T cells appears to be a mainstay of self-tolerance, its role in transplantation tolerance now seems to be less significant. In contrast, extrathymic mechanisms of trans­ plantation tolerance seem to be major factors in long-term graft accept­ ance. If donor antigens are presented in a nonimmunogenic manner on the graft, e.g. due to modification of graft tissue by culture, peripheral T cells of the recipient may ignore the graft. Alternatively, nonstimulatory presentation of donor antigens on graft tissue can induce a state of unre­ sponsiveness in recipient T cells, i.e. anergy, rather than activating them to destroy the graft. Suppression mechanisms also operate to control graft rejection and may be specific or nonspecific in nature. Specific suppression mechanisms might act in an idiotype or antigen-specific fashiom, and evidence is accumulating that this may be mediated through the elab­ oration http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annual Review of Immunology Annual Reviews

Mechanisms of Transplantation Tolerance

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Publisher
Annual Reviews
Copyright
Copyright 1994 Annual Reviews. All rights reserved
Subject
Review Articles
ISSN
0732-0582
eISSN
1545-3278
DOI
10.1146/annurev.iy.12.040194.003423
pmid
8011295
Publisher site
See Article on Publisher Site

Abstract

Transplantation tolerance, the long-term acceptance of grafted tissue in the absence of continuous immunosuppression, remains an elusive goal in humans, but it has been achieved in animal models using numerous approaches. The mechanisms behind graft acceptance vary according to the means used to create the state of acceptance. Several major mechanisms can now be recognized. While thymic deletion of T cells appears to be a mainstay of self-tolerance, its role in transplantation tolerance now seems to be less significant. In contrast, extrathymic mechanisms of trans­ plantation tolerance seem to be major factors in long-term graft accept­ ance. If donor antigens are presented in a nonimmunogenic manner on the graft, e.g. due to modification of graft tissue by culture, peripheral T cells of the recipient may ignore the graft. Alternatively, nonstimulatory presentation of donor antigens on graft tissue can induce a state of unre­ sponsiveness in recipient T cells, i.e. anergy, rather than activating them to destroy the graft. Suppression mechanisms also operate to control graft rejection and may be specific or nonspecific in nature. Specific suppression mechanisms might act in an idiotype or antigen-specific fashiom, and evidence is accumulating that this may be mediated through the elab­ oration

Journal

Annual Review of ImmunologyAnnual Reviews

Published: Apr 1, 1994

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