Immunocompetent cells in amalgam-associated oral lichenoid contact lesions

Inflammatory cells in amalgam-associated, oral lichenoid contact lesions (O LL) were studied in 19 patients by immunocytochemistry using monoclonal ant ibodies. Ten of the patients displayed allergic patch test (PT) reactions t o several mercury compounds and nine were negative. The immunocytochemical quantification showed a uniform composition of the inflammatory mononuclear cells in the two study groups. The number of HLA-D/DR-positive dendritic c ells (P<0.001) and CD1a-positive Langerhans cells (P=0.035) was significant ly lower in the PT-negative than PT-positive patients. HLA-D/DR expression on keratinocytes varied from negative to full thickness staining of the epi thelium. HLA-D/DR expression in the full thickness of epithelium (3) or thr ough the basal and spinous cell layers (2) was seen in 5 of 8 PT-positive p atients, whereas none of the PT-negative patients had this staining pattern (P=0.045). These patients also showed a good clinical response after amalg am removal. Consequently, OLL may represent a true delayed hypersensitivity reaction with a trans-epithelial route of entrance of the metal haptens re leased from dental restorative materials.