Further, Teffs from T1D patients were suppressed to a greater extent by Tregs from the healthy control than by their own Tregs. Taken together, these findings suggest that the reduced regulation observed in autologous co-cultures of cells isolated from T1D patients was due to reduced Treg-mediated suppression intrinsic to the Treg population. Our results are in contrast with previous findings, showing that

responder T cells from T1D were more resistant to suppression [25, 26]. This could be explained by differences in the definition of cellular phenotypes and expansion conditions. While Schneider et al. used adaptive Tregs generated in vitro from CD4+CD25– cells [25], the Tregs used by us in this study were expanded from the

CD4+CD25hiCD127lo CP-673451 price population. In the study by Lawson et al., sorted CD4+CD25hi cells without in-vitro expansion from patients with long-standing T1D were used, and learn more CD127 was not included to discriminate Tregs [26]. Although we have identified a deficient Treg-mediated suppression of polyclonal T cell stimulation in T1D patients who participated in the GAD-alum Phase II trial, treatment with GAD-alum did not affect the suppressive activity of Tregs. It should be kept in mind that samples included in the current study were drawn 4 years after treatment, and that an effect on suppression shortly after treatment cannot be excluded. Furthermore, due to the random selection of patients based on the availability of samples, none of the GAD-alum-treated patients classified as responders to treatment were included in suppression assays [10], and we were thus unable to relate suppression to clinical outcome. Because our assay measures suppression of polyclonal activation, an effect on the specific suppression in response to GAD65 stimulation cannot be excluded. In fact, changes in the frequency of T cells with a Treg phenotype during the trial have been observed only upon GAD65 stimulation [9], while the frequency of Tregs after

culture in medium alone has been similar in GAD-alum and placebo-treated patients throughout the study. Proliferative responses of PBMC from GAD-alum-treated patients in response to GAD65 stimulation were significantly stronger compared HSP90 to placebo in a thymidine incorporation assay, as we have reported previously [12], suggesting that the GAD65-specific responses initiated by in-vitro antigen recall are not anergic. In conclusion, we demonstrate GAD65 recall-induced populations of CD4+CD25hiCD127lo Tregs as well as FSChiSSChiCD4+CD25+CD127+ activated T cells, detectable 4 years after treatment. A deficiency in Treg-mediated suppression detected in T1D patients was intrinsic to the Treg population, but was not affected by GAD-alum treatment.