The composition of T cell subtypes in duodenal biopsies are altered in coeliac disease patients

One of the hallmarks of Celiac disease (CD) is intraepithelial lymphocytosis in the small intestine. Until now, investigations to characterize the T cell subpopulations within the epithelial layer have not discriminated between the heterodimeric co -receptor molecule, CD8 alpha beta, and the possibly immunoregulatory CD8 alpha alpha homodimer molecule. Besides TCR alpha beta+ CD4+ cells, no other phenotypes have been shown to be gluten -reactive. Using flow cytometry on lymphocytes from duodenal biopsies, we determined that the number of B cells (CD3-CD19 +) and the number of CD3+ CD4-CD8-double -negative (DN) T cells were elevated 6-7 fold in children with CD. We next isolated and quantified intraepithelial lymphocytes (IELs) from biopsies obtained from patients (both children and adults) with CD, potential CD and non -CD controls. Flow cytometric analysis of the duodenal T cell subpopulations was performed including the markers TCR alpha beta, TCR gamma delta, CD4, CD8a and CD8 beta. Proportions of gamma delta T cells and CD8 alpha beta+ cells among IELs were increased in CD patients, whereas proportions of CD4+ CD8 alpha alpha+ and CD4+ single -positive T cells were decreased. Additionally, two gluten -reactive T cell lines (TCLs) derived from CD biopsies were analyzed for changes in proportions of T cell subsets before and after gluten stimulation. In a proliferation assay, dividing cells were tracked with carboxyfluorescein succinimidyl ester (CFSE), and both alpha beta and gamma delta T cells proliferated in response to gluten. Changes in duodenal T cell subpopulations in potential CD patients followed the same pattern as for CD patients, but with less pronounced effect.