Background and aims: In coeliac disease, the gut involvement is gluten-dependent. Following the introduction of a gluten-free diet, inflammatory cell infiltration decreases in the small intestinal mucosa. Our hypothesis was that the oral mucosa might mirror the changes found in coeliac disease similarly to the mucosa of the small intestine. Thus, the number of inflammatory cells in the oral mucosa would decrease in patients with coeliac disease on a gluten-free diet.

Methods: The distribution CD45RO+ and CD3(+) T cells, T-cell subpopulations (CD4(+), CD8(+), T-cell receptor (TCR)alpha beta+ and TCR gamma delta+ cells) and HLA DR expression were studied in the buccal mucosa of 15 untreated and 44 gluten-free diet treated coeliac disease patients, and of 19 controls. All 15 patients with untreated coeliac disease were immunglobulin (Ig)A endomysial antibody positive and all 44 patients on gluten-free diet except one were endomysial antibody negative, as were all control subjects.

Results: Untreated coeliac disease patients did not differ from controls in the densities of CD45RO+ cells, CD3(+) cells or of T-cell subsets. In contrast, in treated coeliac disease patients, a significant increase in the numbers of mast cells, CD3(+) and CD4(+) lymphocytes was found in the lamina propria of oral mucosa as compared with patients with untreated coeliac disease and controls. The increase in CD3(+) T cells was in part owing to an increase in lymphocytes expressing no TCR. No differences were found in the expression of human leucocyte antigen (HLA) DR in the epithelium or in the lamina propria in the patient groups studied or in the controls. In treated coeliac disease patients only a few TCR gamma delta+ T cells were found intraepithelially and in the lamina propria, but these cells were not detected in the lamina propria of oral mucosa of patients with untreated coeliac disease or in the controls.

Conclusions: The infiltration of T cells into oral mucosa was increased in treated coeliac disease patients in spite of adherence to a gluten-free diet. Because the CD3(+) T cell count was higher than those of the TCR alpha beta+ and TCR gamma delta+ T cells, there must be other cells involved, probably natural killer (NK) cells. The increase in T-cell subsets in the treated coeliac disease patients seems not to result from poor dietary compliance, but might occur as a late immune response in coeliac disease and reflect chronic immunologic stimulation followed by regeneration of memory T cells.