T lymphocytes, Langerhans cells and HLA-DR expression on keratinocytes in oral lesions associated with amalgam restorations

It has been shown recently that patients with mucosal lesions confined to areas opposing amalgam restorations (contact lesions) show a high rate of allergic reaction towards mercury. These lesions may, therefore, represent a contact hypersensitivity reaction. Contact lesions often have a lichenoid appearance. From a pathogenetic and differential diagnostic point of view we therefore evaluated the presence of lymphocyte subpopulations, Langerhans cells (LC) and the expression of HLA-DR antigens on mucosal keratinocytes in biopsies of contact lesions (Group 1) and in lichen planus lesions with (Group 2) and without (Group 3) partial contact with amalgam restorations. T lymphocytes dominated in all three groups and LC counts were similar. HLA-DR positive keratinocytes were found in 18-36% of lesions in all three groups. Thus, the immunologic parameters examined are not of value in discriminating between the types of lesions studied. Rather, it seems that the pattern observed is a common reaction of the oral mucosa to known (amalgam restorations) and unknown factors.