Abstract
OBJECTIVES: Detection of antigen-specific T cells has been crucial for the study of autoimmune illnesses such as coeliac disease (CD). In CD, an oral gluten challenge is required to expand the rare population of circulating gluten-specific T cells to detectable levels for IFN-γ ELISpot detection. We evaluated interleukin (IL)-2 detection as a simpler approach to identify gluten-specific T cells in CD. METHODS: HLA-DQ2.5+-treated CD adults (n = 10) were assessed before and 6-8 days after commencing a single-bolus gluten challenge. Serum IL-2 (GCIL-2), whole blood IL-2 (WBA) and peripheral blood mononuclear cell IFN-γ ELISpot responses were evaluated. Functional effects of peptides encompassing epitopes of varying immunogenicity and pan-HLA-DQ blocking were tested. RESULTS: GCIL-2 was 90% sensitive in detecting CD. Day 6 post challenge was the optimal day for assessment. In vitro IL-2 release showed higher sensitivity than IFN-γ or IL-10 release in the WBA. IL-2 WBA had 80% sensitivity prior to gluten challenge, and 90% sensitivity at Day 6 post gluten challenge. IFN-γ ELISpot was less sensitive: 20% at baseline and 40% at Day 6 after gluten challenge. Pan-HLA-DQ blocking reduced IL-2 WBA responses by 89-91%, and the assay accurately ranked gluten peptide immunogenicity consistent with published data. CONCLUSIONS: The IL-2 WBA provides superior sensitivity over IFN-γ ELISpot for detecting gluten-specific T cells. It can measure the functional blockade of HLA and accurately reflects gluten peptide immunogenicity hierarchies. The IL-2 WBA supports immunomonitoring and T-cell epitope mapping in CD and offers broad research and clinical application beyond CD.