Increasing evidence have pointed out CD25 as a key molecule during this transdifferentiation process, however molecules that allow such development remain unknown. Collectively, our study unravels a novel immunoregulatory mechanism of NAD+ that regulates Tregs fate while promoting allograft survival that may have clinical applications in alloimmunity and in a wide spectrum Dolasetron of inflammatory conditions. CD4+ CD25+ Foxp3+ natural regulatory T cells (nTregs) play a critical role in the maintenance of immune tolerance and T cell homeostasis in mouse and human1,2. It is well established that Tregs inhibit autoimmunity and inflammation through multiple mechanisms including the production of IL-10. Alternative mechanisms may work through TGF-, known to suppress IFN and T-bet expression, a grasp regulator of T helper 1 (Th1) cells3. Tregs, were first described Dolasetron by Sakaguchi and co-workers4 and have since been recognized as a CD4+ T cell type in both, mice and humans, characterized as CD4+ CD25+ Foxp3+ Tregs constituting a distinct thymus-derived T cell lineage. An additional type of Tregs has been characterized and termed induced regulatory T cells (iTregs). These cells originate in the periphery upon T cell receptor (TCR) stimulation in the presence of TGF-2 as shown in mouse studies. Although many studies have characterized particularly nTregs as a stable lineage, recent observations in mice have challenged this concept5,6. It has been shown that CD4+ CD25+ Foxp3+ cells are comprised of stable (CD4+ CD25highFoxp3+) and unstable (CD4+ CD25lowFoxp3+) populations linked to the expression of the cell surface marker CD257,8. An additional type of Tregs, termed regulatory type 1 (Tr1) cells, has recently been reported in mouse and human experiments9. Tr1 cells have been shown to have the capacity to co-produce IFN and IL-1010. It is well established that IFN-producing cells that co-express IL-10 have immunoregulatory properties that have the capacity to inhibit inflammation, promote transplant tolerance and prevent tissue damage11. More importantly, very recently it has been reported that pro-inflammatory Th17 cells can convert into immunoregulatory Tr1 cells in mice12. Furthermore, increasing evidences point towards the existence of CD4+ T cells that co-express IL-17A and Foxp310,13,14,15. A recent study has shown the importance of CD25 expression levels for the differentiation of CD4+ CD25+ Foxp3+ Tregs into Th17 cells11. Moreover, it has been recently shown that nicotinamide adenine dinucleotide (NAD+), a natural co-factor has the ability to change the binding of IL-2 to CD2516. The role of NAD+ and CD25 in Tregs fate remains however unknown. Here, we investigated the impact of NAD+ around the fate of Tregs. In detail, we characterized the impact of NAD+ around the stability of CD25 while testing the impact on Th17 differentiation. Our study demonstrates that NAD+ favors the conversion of CD4+ CD25+ Foxp3+ Tregs into IL-17A producing cells through purinergic signaling that involves the transcription factor STAT-3. Moreover, NAD+ resulted in a selective depletion of murine CD4+ CD25HighFoxp3+ Tregs that was associated with a transdifferentiation of CD4+ CD25LowFoxp3+ Tregs into IL-17A producing cells exhibiting Th17 cells transcriptional and cytokine profiles. In summary, our study Dolasetron underscores a robust and unique immunoregulatory property of NAD+ with broad anti-inflammatory and immunosuppressive capacities with a wide spectrum of potential clinical applications. Results NAD+ promotes Treg conversion into Th17 cells and their proliferation in absence of TGF-, IL-6, IL-23 and in presence of IL-2 Recent reports have challenged the notion that Tregs represent a stable lineage17. It has been proposed that Tregs may drop Foxp3 expression under specific inflammatory conditions, thus acquiring effector functions17,18. In addition, several Rabbit Polyclonal to ARPP21 studies have shown that Tregs can convert into Th17.