Reply to Comment on "Stability of human rapamycin-expanded CD4+CD25+ T-regulatory cells" Haematologica 2011;96(9):1357-65

Abstract

+ CD25+ T-regulatory cells" Haematologica 2011;96(9):1357-65.We have read the letter by He and Lv 1 and we think the issues raised by the authors are not pertinent to our published work. Specifically, He and Lv raise three issues. 1) They claim that we cannot conclude from our study that rapamycin has an intrinsic role in the stability of Treg cells. We never asserted or even suggested that, based on our data, rapamycin has a direct effect on the stability of Treg cells. Our experiments show that a mixed population of Treg and non-Treg cells cultured for ten days in the presence of rapamycin is stable both in vitro and in vivo. We have never hypothesized a direct effect of rapamycin on Treg cells. Indeed, it was our group who first showed that rapamycin selectively inhibits the proliferation of effector T cells while sparing that of Treg cells 2 and not Strauss et al.,3,4 as wrongly stated by the authors in their comment. Thus, it was us who had demonstrated that rapamycin does not have a direct role on the Treg cells themselves, and these findings were further confirmed in our recent paper in Haematologica.2) He and Lv assert that we cannot claim that rapamycin-expanded Treg cells are stable in vivo since we only showed the frequency of FOXP3