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

Abstract

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.

Keywords: CD4+ T cells; CMV; TCR repertoire; coeliac disease; gluten; regulatory T cells.