Abstract

Regulatory T (Treg) cells play a fundamental role in enforcing peripheral immunological tolerance to self-antigens. Foxp3 has been widely described as a key transcription factor for Treg differentiation and maintenance of their suppressive functions. Upon Foxp3 loss of function mutations, Foxp3-deficient Tregs (∆Treg) develop in the thymus, however, these cells present impaired suppressive capacity and an effector T cell (Teff)-like phenotype. Among the Teff-like characteristics is the shifting of their metabolism towards glycolysis and enhanced mitochondrial respiration. Metabolomic analysis revealed an increase in glutamine consumption. Here, we used 6-diazo-5-oxo-norleucine (DON), a broad inhibitor of glutamine-utilizing enzymes to treat Foxp3 deficient mice (Foxp3∆eGFPiCre), and observed a significant decrease in Teff cell activation, and IFNgamma production from both ∆Treg and Teff cells together with a significant increase in survival. This effect was enhanced when we combined DON treatment with a ∆Treg specific Rictor depletion (Foxp3∆eGFPiCre Rictor∆/∆). Given that glutamine is a key amino acid for T cell activation, we evaluated if this was a pan-T cell effect by inducing Treg depletion in Foxp3DTR mice with concomitant DON treatment. Surprisingly, in the absence of Tregs, DON was not able to prevent autoimmune disease. These results suggest that DON mitigates Foxp3-deficiency mediated disease in a ∆Treg dependent manner, by improving their suppressive capacities. We are currently performing metabolomic studies to better understand the role of glutamine usage in ∆Treg, more specifically if glutamine is directed to glutaminolysis, nucleotide or glutathione synthesis and how this contributes to Treg cell loss of function.