Circulating gluten‐specific, but not CMV‐specific, CD39(+) regulatory T cells have an oligoclonal TCR repertoire

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. DISCUSSION: 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. CONCLUSION: 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.