Transplantation tolerance.

Tolerance has been defined as graft-specific survival in the absence of continued immunosuppression. The mechanisms of central and peripheral tolerance are discussed in this review, as well as the barriers and limitations in achieving graft-specific tolerance. The need remains for definitive laboratory assays to determine the presence of a tolerant state. Genetic biomarker analysis pre-transplant may allow for better donor: recipient matching, lessening the need for immunosuppression, while post-transplant analysis of biomarkers, certain cytokines, and regulatory leukocytes may permit minimally invasive assessment of graft function and potentially, of graft-specific tolerance.