Histochemical identification of T cells in oral lichen planus.

Lysosomal activity was demonstrated in the majority of the lymphocytes forming the mononuclear cell infiltrate in oral lichen planus. Staining for acid phosphatase, N-acetyl-beta-D-glucosaminidase, nonspecific esterase, and beta-glucuronidase was present in these cells in tissue sections, indicating their T cell origin. Small numbers of enzyme-negative lymphocytes were also present. Macrophages showing stronger staining were found scattered through the infiltrates in large numbers. These observations indicate roles for T cells and macrophages in the pathogenesis of lichen planus.