W114 - Islet Autoreactive Regulatory T Cells in Type 1 Diabetes Are Clonally Expanded and Have a Unique TCR Repertoire

Jane Buckner, MD – President, Center for Translational Immunology, Benaroya Research Institute; Janice Chen, MS – Research Technician III, Center for Translational Immunology, Benaroya Research Institute; Aleah DeSchmidt – Research Technician II, Center for Translational Immunology, Benaroya Research Institute; Alex Hu, PhD – Bioinformatician II, Center for Systems Immunology, Benaroya Research Institute; Peter Linsley, PhD – Member, Center for Systems Immunology, Benaroya Research Institute; Emma Mortensen – Research Technician II, Center for Translational Immunology, Benaroya Research Institute; David Rawlings, MD – Director, Center for Immunity and Immunotherapies, Seattle Children's Research Institute; Cate Speake, PhD – Research Assistant Member, Center for Interventional Immunology, Benaroya Research Institute; Soo Jung Yang, PhD – Research Assistant Member, Center for Translational Immunology, Benaroya Research Institute

Abstract Text: Autoimmune type 1 diabetes (T1D) results from unrestrained destruction of pancreatic islets by autoreactive T cells, but little is known about islet autoreactive (IAR) regulatory T cells (Treg) in T1D. We analyzed IAR CD4 conventional T (Tconv) cells and Treg in the blood from 10 established DRB1*0401 T1D subjects and 10 matched healthy controls using a CD154-CD137 activation assay combined with single cell RNA-sequencing to capture the TCR repertoire and transcript profiles in parallel. We found no difference in the frequency of IAR CD4 Tconv or Treg between T1D subjects and healthy controls, nor was there a difference in Treg/Tconv ratio. However, the transcript profiles of IAR Treg from T1D subjects differed from controls, with reduced expression of genes involved in signaling, metabolism, biosynthesis, and regulation of cell proliferation. Clonal expansion of IAR Tconv and Tregs was detected within T1D and control donors, but the TCR repertoire was unique for each cell type. Sharing of TCRα chains between donors was observed primarily in IAR CD4 Tconv cells, however, TCRα chains from both cell types were shared with TCRs from pancreatic islets. Gene edited Tregs expressing an IGRP-specific Treg TCR mediated robust antigen-specific and bystander suppression of CD4 Tconv cells. Thus, circulating IAR Tregs numbers are not reduced in T1D donors and show evidence of antigen driven expansion. While their TCR repertoire is unique from IAR Tconv cells, circulating IAR Treg share TCR chains with pancreatic TCRs and can mediate robust suppression.