DISTRIBUTION OF INTERFERON-GAMMA MESSENGER-RNA-POSITIVE CELLS IN ORALLICHEN-PLANUS LESIONS

The present study investigated the potential involvement of interferon -gamma (IFN-gamma) producing cells in the pathogenesis of oral lichen planus (OLP). On biopsies from 10 OLP patients, an in situ hybridizati on technique was employed to determine the topographical distribution of cells expressing IFN-gamma mRNA. It was estimated that approximatel y 1% or fewer lesional cells were IFN-gamma mRNA-positive. These cells were mainly encountered lining the basal membrane in a majority of th e patients, or were in a few cases circumscribing the infiltrate, but were more seldom localized to the center of the lesion. A slightly hig her, but not statistically significant, number of phytohemagglutinin ( PHA)-induced IFN-gamma-producing cells, in vitro, was found in blood f rom 11 other OLP patients compared with blood from matched controls. E qual concentrations of IFN-gamma in supernatants from PHA-stimulated b lood cells were detected in the two groups. Similarly, the IFN-gamma r esponse towards C. albicans was alike in OLP and in healthy control (H C) blood cells, indicating normal immunological memory function in the OLP patients. A small set of cells with spontaneous IFN-gamma product ion was found in OLP and in HC peripheral blood. The data suggest that T-lymphocyte activation and cytokine production act locally and are n ot reflected in peripheral blood. The localization of the IFN-gamma mR NA-positive cells indicates that the antigenic peptides are presented at the periphery of the mononuclear cell infiltrate. Furthermore, the low frequency of IFN-gamma mRNA-positive cells in the lesions suggests that the disease is maintained by a small number of antigen-specific T cells.