Preservation of C-peptide secretion was still present in a 4-year follow-up to the Phase II trial [11], and induction of a T cell subset with memory phenotype was observed upon GAD65 stimulation [12]. Here we demonstrate that a great majority of lymphocytes in this T cell subset with memory phenotype expressed

FoxP3 and high levels of CD25. Although some differences in the experimental setup were introduced in the present study, the main difference being that PBMC were cultured for 72 h at 21 and 30 months and for 7 days at the 4-year follow-up, the increased frequencies of CD25hi and FoxP3+ cells detected in this 4-year follow-up of the study are in agreement with our previous findings at 21 and 30 months after treatment [9]. In the present study, the CD127

and CD39 markers small molecule library screening were included to further define Tregs. Both CD4+CD25hiCD127lo and CD4+CD25+CD127+ cells were expanded by GAD65 stimulation, but a higher proportion of FSChiSSChi CD4+ cells were CD127+ than CD127lo/–, suggesting that the frequency of T cells with both Treg and activated-non-Treg phenotype increased following GAD65 stimulation. Expression of CD39, an ectonucleotidase expressed on a subset of Tregs which hydrolyzes ATP into adenosine monophosphate (AMP) [23, 29], was also increased upon antigen recall in GAD-alum-treated patients. It has been postulated that removal of proinflammatory ATP could be a suppressive mechanism mediated by CD39 on Tregs. In a recent study, CD39+ PR-171 clinical trial but not CD39–CD4+CD25hi cells were able to suppress IL-17 production [30]. As the levels of IL-17 were undetectable in the supernatants of both expanded Teffs and Teff/Treg cultures, we cannot draw any conclusion on the ability of Tregs to suppress production of this cytokine in our settings. However, we have shown previously that secretion of IL-17, along with that of several other cytokines, was increased by GAD65 stimulation in PBMC supernatants [12]. Although the current study PtdIns(3,4)P2 does not include

healthy subjects, the expression of CD39 on resting CD4+CD25hiCD127lo cells detected by us in these T1D patients seems to be lower than what has been reported in healthy individuals by others using the same anti-CD39 clone and fluorochrome [30]. In line with previous findings [31], expanded CD25+CD127lo Tregs were suppressive and retained their phenotype after expansion and cryopreservation. Although we were able to sort, expand and assess suppression in a limited number of individuals, there was no readily evident difference in the suppressive capacity of Tregs between placebo and GAD-alum-treated patients 4 years after administration of the treatment. Cross-over culture experiments revealed that Tregs isolated from patients with T1D participating in the GAD-alum trial had an impaired suppressive effect on autologous Teffs and also on Teffs from a healthy individual.