Ultrastructural demonstration of Fc gamma-receptors in sarcoid skin lesions.

Immune complexes of horseradish peroxidase oxidase (HRP) and rabbit IgG antibodies to HRP were used to study the Fc gamma-receptors in granulomas of cutaneous sarcoidosis. Cryostat sections of skin biopsies were incubated with HRP-anti-HRP, and the peroxidase activity was demonstrated with 3,3-diaminobenzidine tetrahydrochloride and H2O2. Most cells in the granulomas, both epithelioid and giant cells, were stained. By electron microscopy, the reaction products were localized to the plasma membranes of the cells as well-defined granular deposits. No reaction product was demonstrated intra- or extracellularly.