Immunoelectron-microscopical localization of in vivo-bound complement C3 in bullous pemphigoid with the use of the peroxidase-antiperoxidase multistep technique.

In vivo-bound complement C3 in bullous pemphigoid was precisely localized by means of the peroxidase-antiperoxidase multistep technique. In the nonbullous lesions peroxidase deposits filled the lamina lucida completely, i.e., the space between lamina densa and the cell membranes of the basal cells. In developed bullae, the reaction product was located both on the lamina densa and on the surface of separated keratinocytes. These findings may indicate that antigen components in bullous pemphigoid are localized almost exclusively within the ground substance which fills the lamina lucida and covers the surface of the basal cells.