Immunohistochemical findings in the jejunal mucosa of patients with coeliac disease.

In the pathogenesis of coeliac disease, disturbed immunological processes play a basic role. This is also proved by immunohistochemical findings in the jejunal mucosa of patients with this disorder, which are discussed in this review. Intraepithelial lymphocytes are increased in number in active coeliac disease, most being of the CD8 subpopulation. The counts of lamina propria lymphocytes and the relative numbers of their subsets are comparable to those in healthy controls, but several studies have indicated that the densities of IgA, IgM and IgG immunoglobulin-containing cells in the lamina propria are increased in untreated coeliac disease. Activated T cells can also be found in the lamina propria of patients on gluten-containing diets. In the crypt epithelial cells of coeliac patients on normal diets, strong expression of HLA Class II antigens can be observed. All of these changes are normalized on a gluten-free diet. It was recently discovered by the authors and others that one of the hallmarks of coeliac disease, both active and treated, is an increase in number and proportion of gamma/delta intraepithelial T lymphocytes. The permanent increase of gamma/delta T cells may facilitate identification of a coeliac patient also when an intestinal biopsy is taken on a gluten-free diet and other morphologic signs are normalized. The detection of elevated numbers of intraepithelial gamma/delta T cells is also an indispensable help in the diagnosis of latent coeliac disease.