Immunohistochemical analysis of cells in mucosal lesions of oral lichen planus

We immunohistochemically analyzed the immunological background of the pathogenesis of oral lichen planus (OLP). Abundant lymphocytes infiltrated OLP mucosal lesions, particularly in satellite cell necrosis (SCN) regions, and cytotoxic/suppressor T lymphocytes were predominant in seven of 10 OLP cases. Some carried IL‐2 receptors, particularly in SCN. Keratinocytes of the mucosal lesions expressed both HLA‐ABC and HLA‐DR antigens. This suggests that activated cytotoxic/suppressor T lymphocytes may play a major role in cytotoxity to keratinocytes as effector cells in OLP. OKM1‐, OKM5+, HLA‐DR+ and IL‐1+ cells, vascular endothelial cells and clusters of spindle‐shaped or oval cells, which had the same surface characteristics as a monocyte macrophage subset, were abundant and, together with migrating lymphocytes, might play a role in the immune response in mucosal lesions of OLP.