An immunohistochemical study of oral lichen planus.

Specimens from 22 cases of oral lichen planus were prepared for studies of the basement membrane zone by immunohistochemical and histochemical methods. Langerhans' cells, monocytes, and lymphocytes constitute the predominant cells of the inflammatory infiltrate, thus indicating a cell-mediated response. Lymphocyte-related necrosis of epithelium and nonspecific vasculitis are associated with an altered basement membrane zone. Immunoproteins, including IgG, IgA, IgM, and C'3 as well as fibrinogen, are present and distributed in a nonspecific pattern.