Summary

The significance of islet Ag-reactive T cells found in peripheral blood of type 1 diabetes (T1D) subjects is unclear, partly because similar cells are also found in healthy control (HC) subjects. We hypothesized that key disease-associated cells would show evidence of prior Ag exposure, inferred from expanded TCR clonotypes, and essential phenotypic properties in their transcriptomes. To test this, we developed single-cell RNA sequencing procedures for identifying TCR clonotypes and transcript phenotypes in individual T cells. We applied these procedures to analysis of islet Ag-reactive CD4+ memory T cells from the blood of T1D and HC individuals after activation with pooled immunodominant islet peptides. We found extensive TCR clonotype sharing in Ag-activated cells, especially from individual T1D subjects, consistent with in vivo T cell expansion during disease progression. The expanded clonotype from one T1D subject was detected at repeat visits spanning >15 mo, demonstrating clonotype stability. Notably, we found no clonotype sharing between subjects, indicating a predominance of "private" TCR specificities. Expanded clones from two T1D subjects recognized distinct IGRP peptides, implicating this molecule as a trigger for CD4+ T cell expansion. Although overall transcript profiles of cells from HC and T1D subjects were similar, profiles from the most expanded clones were distinctive. Our findings demonstrate that islet Ag-reactive CD4+ memory T cells with unique Ag specificities and phenotypes are expanded during disease progression and can be detected by single-cell analysis of peripheral blood.

Overall design

This project contains RNA-seq files from four cell types: 1) T cell clone (N=149 single cell profiles); 2) T cell clone (N=9 bulk cell profiles); 3) CD8+ influenza-reactive T cells (N=45 single cell profiles); and 4) CD4+ pooled islet antigen-reactive T cells (N=246 single cell profiles).

Contributors

Karen Cerosaletti 1, Fariba Barahmand-Pour-Whitman 2, Junbao Yang 3, Hannah A DeBerg 2, Matthew J Dufort 2, Sara A Murray 2, Elisabeth Israelsson 2, Cate Speake 4, Vivian H Gersuk 2, James A Eddy 2, Helena Reijonen 4, Carla J Greenbaum 4, William W Kwok 3, Erik Wambre 3, Martin Prlic 5, Raphael Gottardo 5, Gerald T Nepom 6, Peter S Linsley 7

Contact

To be supplemented.