Does the epithelium play a central role in the immune function of rhinopharyngeal tonsils? An immunocytochemical and ultrastructural study.

Enlarged adenoids from 10 children with chronic rhinitis and otitis media with effusion have been studied immunocytochemically and ultrastructurally, to better define the possible role of the epithelium and the dendritic accessory cells in the immune activation of lymphoid cells, and provide further insight into the pathogenesis of the disease. The presence within the columnar epithelium of lymphocytes positive for CD8 antigen, and which electron microscopically have been found frequently apposed to degenerating epithelial cells suggests that the latter cells are targets for cytotoxic activity of intraepithelial lymphocytes, rather than being engaged in antigen presentation. Furthermore, the finding of typical dendritic accessory cells, recognized by their typical immunophenotypic and ultrastructural features, in the lamina propria, indicates that antigen presentation is more likely exerted by dendritic accessory cells. This is further supported by the fact that these cells express major histocompatibility (MHC) class II molecules, which are needed for antigen presentation, whereas epithelial cells do not. A possible relationship between epithelial damage and the pathogenesis of adenoidal enlargement is discussed.