The microenvironment of coeliac disease: T cell phenotypes and expression of the T2 'T blast' antigen by small bowel lymphocytes.

Peroral jejunal biopsies were studied by double-label immunofluorescence on cryostat tissue sections from control patients of normal histology and patients with coeliac disease. A panel of monoclonal antibodies was used to identify T cells and T cell subsets, together with antibody markers of cell stimulation (the T2 40 kdalton T blast specificity), proliferation (T9 and Ki67) and activation (HLA-DR and Ig receptors). In normal mucosa, expression of T2 was predominantly found in the T8+ intraepithelial cytotoxic/suppressor population. In coeliac disease there was little alteration of T4:T8 ratios per se, but a much higher percentage of T8-T4+ helper/inducer cells expressed the T2 antigen (approx. 30% compared to approx. 10%), manifest as an accretion of T2+T8- cells in the epithelium and subjacent stroma. Additionally, T cell lymphoid aggregates were observed in the lamina propria, consisting of greater than 90% T4+ cells, of which the majority (60-80%) were also T2+. The increase of stimulated helper cells correlated well with the pathology of coeliac disease, being most marked in untreated cases of maximal tissue damage, and least in well treated cases with restoration of normal morphology. By contrast, an increased tendency for the T8+ cells to co-express T1 in untreated coeliac disease was not observed in treated disease, even in cases where failure to adhere to a strict gluten free diet had resulted in little histological improvement. There was little evidence of T cell activation or proliferation. The observation that T helper cells undergo migration and stimulation suggests an imbalance in immunoregulation which causes a breakdown of normal immune tolerance to dietary gluten, and therefore may be a crucial mechanism of tissue damage in coeliac disease.