In situ identification of mononuclear cells in cutaneous infiltrates in discoid lupus erythematosus, sarcoidosis and secondary syphilis.

The inflammatory mononuclear cell infiltrates observed in lesional skin from patients with discoid lupus erythematosus (DLE), sarcoidosis, and secondary syphilis have been characterized in situ. Immunological markers (human T lymphocyte antigens and receptors for sheep erythrocytes, C3b, C3d and Fc gamma) were studied by using immunofluorescence tests with IgG F (ab')2 preparation of anti-T lymphocyte serum, hemadsorption with tissue sections, and tests with soluble immune complexes of peroxidase. In DLE, T lymphocytes were the dominant cell type. In sarcoidosis, the epithelioid cells, including giant cells, had markers similar to macrophages. The lymphohistiocytic cells consisted mainly of macrophages, some T lymphocytes and a few B lymphocytes. In secondary syphilis (condylomata lata), macrophages and T lymphocytes were the dominant cell types, and relatively few B lymphocytes were detected.