Immunohistochemical staining of Langerhans cells and macrophages in oral lichen planus.

Twenty patients with clinically and microscopically confirmed lichen planus were studied immunohistochemically. Monoclonal antibody to HLA-DR antigens and polyclonal antisera to S-100 protein and muramidase were applied to paraffin-embedded sections for the purpose of elaborating on the pathogenesis of this disease. Trypsin incubation of sections was also done in order to determine its effect on immunostaining. Langerhans cells were identified with anti-S-100 and anti-HLA-DR, and macrophages were identified with antimuramidase and anti-HLA-DR. Keratinocytes also expressed HLA-DR membrane activity in lichen planus tissue. Trypsinization significantly improved the expression of S-100 protein and muramidase antigens. It was concluded that Langerhans cells, macrophages, and keratinocytes play important roles in antigen processing and/or phagocytosis during the natural history of this disease.