Human melanocytic naevi. III. Immunofluorescence and immunoelectron microscopy of the basement membrane zone.

Serum pemphigoid antibody (BPA) was used to demonstrate the intraepidermal location of human pigmented naevi. Immunofluorescence was predominant along the epidermal-dermal junction and around the naevus nests seemingly located in the dermis. Serial sections showed that these naevus nests were intraepidermal. The immuno-gold labelling technique for electron microscopy, was improved by using uranyl acetate with no osmium tetroxide or lead citrate. Hemidesmosomes were absent from the epidermal-dermal junction apposed to naevus nests. Gold labelling occurred in patches of particles along the lamina densa. The number of gold particles per micron length of lamina densa were quantitated. Immunofluorescence microscopy and immuno-gold electron microscopy confirmed the intraepidermal location of pigmented naevi.