Cutaneous lymphocyte associated antigen (CLA) and alpha e beta 7 integrins are expressed by mononuclear cells in skin and oral lichen planus.

The cutaneous lymphocyte associated- (CLA-) positive subset of lymphocytes appears to migrate preferentially into skin by interacting with E-selectin on vascular endothelium; lymphocytes expressing the alpha e beta 7 integrin accumulate preferentially in the epithelium of the gastrointestinal tract. To determine whether the mononuclear cell population of the oral mucosa resembles that of the skin or intestine, and using lichen planus as a model, the proportions of CLA- and alpha e beta 7-positive cells in the epithelium, lamina propria and peripheral blood were compared by immunostaining and flow cytometry. In both skin and oral lichen planus, selective accumulation of CLA-positive cells was seen in the epithelium but not in the lamina propria. In contrast, large numbers of alpha e beta 7-positive intraepithelial cells were found in oral but not in skin lichen planus. These results show that in terms of CLA and alpha e beta 7 expression there are important differences in the mononuclear cell population of oral mucosa and skin.