Tacrolimus has been shown to downregulate FOXP3 expression, whereas TSDR demethylation remained stable in allograft recipient patients.6,19 In keeping with these findings, we observed that the percentage of CD25int mTreg and naive Treg cells (Figure 3A) with demethylated TSDR was not different between cells expanded in TAC or DMSO control containing media. In contrast, cells expanded with TAC showed reduced FOXP3 expression in naive Treg and CD25int mTreg cell populations (P < 0.01, P < 0.05, respectively; Figure 3B).