Circulating gluten-specific, but not CMV-specific, CD39 regulatory T cells have an oligoclonal TCR repertoire.

Understanding the T cell receptor (TCR) repertoire of regulatory CD4 T-cell (Treg) populations is important for strategies aiming to re-establish tolerance in autoimmune diseases. We studied circulating deamidated gluten-epitope-specific CD39 Tregs in patients with coeliac disease following an oral gluten challenge, and we used cytomegalovirus (CMV)-specific CD39 Tregs from healthy controls as a comparator population.We used the OX40 assay to isolate antigen-specific Tregs by induced surface co-expression of CD25, OX40 and CD39. RACE PCR amplification and Sanger sequencing of the TCR β chain were used to analyse repertoire diversity.We found that, following oral gluten challenge, circulating gluten-specific CD39 Tregs had an oligoclonal TCR repertoire that contained public clonotypes. Conversely, the TCR repertoire of CMV-epitope-specific CD39 Tregs from healthy controls was polyclonal.These data indicate that a biased TCR repertoire is not inherent to CD39 Tregs, and, in this case, is apparently driven by the HLA-DQ2.5-restricted deamidated gluten peptide in coeliac disease patients.This is the first assessment of the TCR repertoire within circulating human Tregs specific for foreign antigen. These data enhance our understanding of antigen-specific CD4 responses in the settings of chronic inflammation and infection and may help guide immunomonitoring strategies for CD4 T cell-based therapies, particularly for coeliac disease.