Antigen discovery for regulatory T cells (Tregs) in type-1 diabetes (T1D)

Antigen specific Tregs are more efficient than polyclonal Tregs in their suppressive capacity, which makes them attractive tools for further targeted tolerogenic therapy. Autoreactive T cells specificity has been well characterized in type 1-diabetes but little is known about autoreactive Treg specificity. Whether Tregs recognize the same tissue-specific self-antigens as autoreactive T cell, or they recognize different self-antigens to regulate local immune responses via bystander suppression is unclear. Our goal is to identify antigen specificity from enriched islet infiltrated Treg by using previously validated peptide-major histocompatibility complex (pMHC) library displayed on yeast. We first performed single cell TCR sequencing on Tregs from the pancreatic islet of 12 weeks old NOD mice. Data show an abundance of the TCR allele TRAV5D4 usage in islet infiltrated Tregs that has been characterized to target a primary insulin peptide. Moreover, we also performed single cell RNAseq together with TCR sequencing on islet infiltrated CD4+ T cells from a T1D patient from the Network for Pancreatic Organ Donors with Diabetes. We were able to identify enriched TCRs with Treg gene expression profile that will be used to screen for antigen recognition on a DR4 pMHC yeast library. New antigen identification for pancreatic islet-infiltrated Tregs will allow us to improve our understanding of Treg deficiencies in T1D and may lead us to design new immunosuppressive therapies.