Light and fluorescent microscopic studies of recurrent aphthous ulcers.

Tissue from seventeen patients with recurrent aphthous ulcers was studied by light and immunofluorescent microscopy to characterize changes in the inflammatory infiltrate throughout the evolution of the lesion. Enzyme histochemical studies and immunoperoxidase stains for immunoglobulin revealed that monocytes and histiocytes form a large proportion of the infiltrate in the early phase of the ulcer and that most lymphoid cells present are of T-cell origin. Immunoglobulin-bearing lymphocytes and plasma cells are sparse at all stages. Direct immunofluorescent studies were frequently positive; however, no consistent pattern was noted.