Identification of mononuclear cells in situ in skin lesions of lichen planus.

Cryostat sections of lesional skin of lichen planus were examined for receptors for sheep erythrocytes (T lymphocytes), Fcgamma and C3b receptors (B lymphocytes and macrophages) and C3d (B lymphocytes). The indicator cells were applied using a closed chamber technique. The combination of the closed chamber technique and treatment of the sheep erythrocytes with a strong sulphydryl reagent enabled us to detect T lymphocytes by their membrane receptors in situ. T lymphocytes were the predominant mononuclear cells in the dermal infiltrate, with less macrophages and only a few B lymphocytes.