[Regulatory T cell based transplant tolerance--freedom from immunosuppression].

Tolerance after clinical transplantation (Tx) is still extremely rare. However, Kyoto elective protocol enabled a substantial number of patients to weaned off immunosuppression after liver Tx. This is referred to as an immunoprivilege. Nevertheless, the operating mechanisms for liver Tx tolerance remain elusive. The authors demonstrated that regulatory T cells (Tregs) are likely to play an important role in liver Tx tolerance. In addition, we found that precursor like Tregs exist in the human peripheral blood. This can propagate upon stimulation with allo-antigen, in contrast to anergic property of Tregs. Thus, the exploitation of precursor like Tregs as a cellular source of ex vivo and in vivo expansion may lead to the widespread clinical use of Tregs for Tx.