An electron microscopic study on the aetiopathogenesis of recurrent aphthous ulcers of the oral mucosa. The fine structure of mucosal lymphocytes, reticular or reticuloid cells, macrophages and basal epithelial cells.

The present report is concerned with the immunopathogenesis of recurrent aphthous ulcers (RAU). Lymphocytes in various stages of sensitization are described and their interaction with macrophages, each other and epithelial cells. Typical macrophages were seen in the lamina propria but not in affected epithelium. The phagocytic cells seen between epithelial cells and in the juxtabasal part of the lamina propria was identified as a reticuloid cell because of close connections with each other, numerous microvesicles and electron-lucent (euchromatic) nuclei. It is thought that it replaces the macrophage seen in Behçet's syndrome and oral lichen planus and is responsible for the localized nature of RAU.