The road toward transplantation tolerance

Calcineurin inhibitor minimization in pediatric liver allograft recipients

The use of CNI in pediatric LTx has dramatically improved the outcome for children with end-stage liver disease by significantly reducing the rate of acute and chronic rejection. Long-term concerns about CNI-induced nephrotoxicity and other adverse effects remain an issue, particularly as the emphasis moves from short-term survival to long-term quality of life. This review summarizes lessons learnt from pediatric and adult solid organ transplantation in minimizing CNI use in immunosuppression protocols in children following LTx. There are three models for CNI minimization: dose reduction, withdrawal or avoidance, supplemented by the use of IL-2 receptor blocking antibodies in the peri-transplant period, and early transition to alternate drugs such as MMF or SRL. Prospective studies evaluating reduction or withdrawal protocols in adult and pediatric LTx indicate that rejection rates are comparable with traditional CNI-based immunosuppression and that two and five yr patient and graft survival are similar, with recovery in renal function. There are few studies evaluating complete avoidance of CNI, apart from that in renal transplantation, although the benefits of long-term reduction in cardiovascular, metabolic, and possibly neoplastic side effects may justify this approach. It is not clear yet how CNI minimization will affect the development of tolerance but experimental and preliminary clinical studies indicate that CNI and steroid avoidance or minimization in the peri-operative period may favor the development of long-term graft tolerance. In summary, CNI minimization may be safe and effective in the short term but large-scale pediatric randomized studies are required to evaluate the long-term efficacy of these regimes in the development of chronic rejection, PTLD, and graft tolerance.

Immunosuppression: towards a logical approach in liver transplantation

Over the last two decades there has been a significant increase in the number and types of immunosuppressive agents that have been available to clinicians. The protocols for immunosuppression used in liver transplantation have been derived historically from those in renal transplantation. During the last decade there has been a shift in the use of immunosuppression, with the introduction of interleukin (IL)-2 receptor antagonists in place of anti-lymphocyte preparations, substitution of tacrolimus for cyclosporin and mycophenolate for azathioprine. The use of corticosteroids has been reduced. For a variety of reasons, these changes have not always been made on the basis of properly randomized studies. The place of newer agents, such as sirolimus and leflunomide derivatives and of the microbiological agents, is unclear. In this review, we outline briefly the mechanism of action of drugs and suggest possible approaches to the management of the liver allograft recipient, suggesting how treatment could be adjusted according to the indication for transplantation as well as the individual's comorbidities.