Diabetes and other autoimmune endocrine diseases
Self-reactive T-cells can be found in both healthy individuals and individuals with autoimmune disease. To identify unique characteristics and clonality of islet antigen reactive memory CD4 T cells that relate to type 1 diabetes (T1D), we coupled CD154 enrichment of islet antigen specific T cells with novel single-cell RNA-seq and recombinant T cell receptor (TCR) expression methods. We detected predominantly private TCR clonotypes (α/β pairs) with increased clonal expansion in islet antigen reactive CD4 memory T cells in established (stage 4) T1D subjects compared with healthy controls matched for HLA, age and gender. To assess patterns of islet antigen recognition between individuals we developed viral expression of recombinant TCR sequences and performed functional assays to identify the specific islet peptides recognized by individual TCRs. Re-expression of expanded TCRs from multiple T1D subjects identified IGRP, and GAD as antigenic target in T1D subjects after diagnosis, implicating these molecules as trigger for islet antigen-reactive CD4+ T cell expansion. Current expanded studies involve comparing binding properties of islet-antigen specific TCRs to TCRs specific for foreign antigens. Characterization of recombinant TCR specificities will enable us to understand how the level of islet antigen-reactive T cells and their antigenic specificities change during disease progression and therapeutic intervention, and how to utilize these T cells as biomarkers and therapeutic targets.