Direct cloning and tetramer staining to measure the frequency of intestinal gluten-reactive T cells in celiac disease.

Knowledge of the frequency of disease-driving CD4⁺ T cells in lesions of chronic human inflammatory diseases is limited. In celiac disease (CD), intestinal gluten-reactive CD4⁺ T cells, which recognize gluten peptides only in the context of the disease-associated HLA-DQ molecules, are key pathogenic players. By cloning CD4⁺ T cells directly from intestinal biopsies of CD patients, we found that 0.5-1.8% of CD4⁺ T cells were gluten reactive. About half of the gluten-reactive T cells were specific for either the immuno-dominant DQ2.5-glia-α1a or DQ2.5-glia-α2 epitopes, suggesting that direct visualization of gluten-specific T cells could be possible. Assessed by flow cytometry, tetramer-positive T cells were present in 10/10 untreated CD patients with a frequency of 0.1-1.2% of CD4⁺ T cells. Gluten-specific T cells were also detectable in most treated CD patients (7/10). Moreover, the frequency of gluten-specific T cells correlated with the degree of histological damage in the gut mucosa as scored by Marsh-grading, and also with serum IgA anti-transglutaminase 2 antibody levels. Tetramer staining of gluten-reactive T cells in biopsy material is a useful tool for future studies of such cells in CD and could also potentially serve as a diagnostic supplement in selected cases.