T cell suppression in transplantation tolerance through linked recognition

Area of Science:

• Immunology
• Transplantation Biology
• Tolerogenic Mechanisms

Background:

• Allogeneic tissue grafts are often accepted indefinitely in mice treated with CD4- and CD8-specific antibodies, indicating induced immunologic tolerance.
• While tolerance to minor histocompatibility antigens is established, some third-party grafts are unexpectedly accepted or rejected slowly, suggesting complex suppressive mechanisms.

Purpose of the Study:

• To investigate the hypothesis that accepted third-party grafts share antigens with the original tolerizing graft, making them targets for suppressive CD4+ T cells.
• To elucidate the role of linked recognition in the suppression of graft rejection within a tolerized host.

Main Methods:

• Mice were tolerized to a specific set of minor antigens (B10 minors).
• Tolerized mice were challenged with third-party grafts expressing these B10 minors plus a strong transplantation antigen (H-2Kb).
• The effect of linking the H-2Kb antigen to the B10 minors on an F1 graft was assessed for rejection rates.

Main Results:

• Grafts containing both the original minor antigens and the H-2Kb antigen were significantly less rejected in tolerized mice compared to naive mice.
• Rejection of the third-party graft was impaired when the strong transplantation antigen was "linked" to the previously tolerated minor antigens.
• Suppression appears to operate locally, possibly on the same antigen-presenting cell, via a mechanism of linked recognition.

Conclusions:

• Suppression of transplant rejection in tolerized mice can operate locally through linked recognition of antigens.
• Linked recognition of antigens may extend immunologic tolerance to previously non-tolerized third-party antigens.