Tolerance studies in liver transplantation: are we fooling ourselves?

Purpose of review This article will summarize outcomes of prior immunosuppression withdrawal trials in pediatric and adult liver transplantation and provide updates on the current status of ongoing clinical tolerance studies including evolving strategies, such as identification of reliable biomarkers or immunomodulation to achieve an earlier onset and more robust level of operational tolerance. Recent findings Clinical tolerance studies in liver transplantation have previously been limited by inconsistent and delayed success of immunosuppressive withdrawal, lack of substantial histological analysis from liver tissue biopsy, and the inability to translate mechanistic studies to reproducible clinical outcomes. Current clinical trials are attempting to overcome these hurdles through more comprehensive and guided immunosuppression withdrawal protocols. Novel and emerging technologies are enabling investigators to identify and validate potential biomarkers of tolerance in order to predict patient subpopulations disposed towards operational tolerance. Immune cell therapy using the adoptive transfer of various cell products have been shown to be feasible and well tolerated in early phase clinical trials and ongoing. Tolerance studies in liver transplantation are evolving and substantial progress has been made in overcoming the challenges that have prevented the widespread implementation of immunosuppression withdrawal protocols in the clinic. Identifying more sensitive and specific predictors of immunosuppression withdrawal success and tolerance induction strategies that will allow for early tolerance will advance the field tremendously towards the goal of promoting long-term allograft survival without immunosuppression.