Herpes gestationis: ultrastructural identification of the extracellular antigenic sites in diseased skin using immunogold techniques.

Using a direct immunogold technique, we studied the level of immunological events in the skin basement membrane in a patient with herpes gestationis during blister formation. Within the lamina lucida, IgG and C3 were localized beneath the basement membrane of basal keratinocytes, 30-40 nm above the lamina densa. In many areas of blister formation sub-basal dense plates, but probably also the upper parts of the hemidesmosomes were separated from the roof of the blister. In the perilesional lamina lucida and in the blister, IgG and C3 containing amorphous grains, most probably immunocomplex aggregates, were detected. They covered the basement membrane of keratinocytes and left free a 30-40 nm band above the lamina densa. Our study indicates that in herpes gestationis the cleavage, accompanied by IgG, C3 and immunocomplex deposition, occurs at the level of the sub-basal dense plate. However, cleavage through upper hemidesmosomal structures can occur in parallel. These data further support the involvement of hemidesmosomes in the pathogenesis of the disease and therefore in its relationship to bullous pemphigoid.