We show that a naive Treg population may be sorted using surface markers and expanded to comprise a promising option for future studies to adoptively transfer Treg cells to tolerize an allograft. Despite some loss of Treg function in the presence of TAC, this population of cells nevertheless retains a high degree of suppressive function and importantly retains a TSDR demethylated status after expansion. This study indicates that sorting a population of naive Treg cells according to a CD4+CD45RA+CD25intCD127−/lo will improve therapy beyond sorting the whole CD4+CD25+CD127lo total Treg cell population. Future work may identify if sorting a mixture of naive Treg and CD25hi mTreg will further enhance the production of a suitable Treg population for cellular therapy. Analysis of suppressive function in a freshly isolated nonexpanded total Treg cell population in patients undergoing haemodialysis showed a reduced suppressive function compared with healthy controls.24 Future studies may establish if the naive Treg population that we examined here has reduced capacity to suppress compared with the same population obtained from healthy subjects.