T cell subsets and Langerhans cells in lichen planus: in situ characterization using monoclonal antibodies.

Skin biopsies from four patients with lichen planus were studied using monoclonal antibodies directed against T lymphocytes. Anti-TI and anti-T3 antibodies, which react with all peripheral T cells, stained most cells in the dermal infiltrates. The majority of infiltrating cells also stained with anti-T4 and anti-T4b antibodies, which react with helper/inducer cells, whereas a minority of cells stained with anti-T8 antibody, which reacts with cytotoxic/suppressor cells. Surface IgM was not identified on any infiltrating cells, providing evidence against B cell participation. Intraepidermal and dermal cells with long cytoplasmic extensions stained with any anti-T6 antibody in all cases, defining them as Langerhans cells or their precursors. T6-positive cells were seen in greater number than in normal control epidermis and dermis. The results indicate that well-developed lesions of lichen planus are characterized by an influx of helper/inducer T lymphocytes and increased numbers of Langerhans cells. These observations support the contention that cellular immunity is important in the pathogenesis of this disorder.