Restriction of Cicatricial Pemphigoid Antigens to the Lamina Densa: Confirmation by Indirect Immunoelectron Microscopy

Circulating anti-basement membrane zone (BMZ) antibodies in a patient with cicatricial pemphigoid (CP) were examined using an indirect immunofluorescence test, indirect immunoperoxidase electron microscopy, and Western blot analysis. An indirect immunofluorescence test on salt-split skin revealed that the anti-BMZ antibodies reacted solely to the dermal side at the separating epidermal-dermal interface, and indirect immunoelectron microscopy on intact skin indicated localization of the corresponding antigens (CP antigens) over the lamina densa and within the lower half of the lamina lucida; there were no CP antigens beneath a melanocyte. Indirect immunoelectron microscopy on salt-split skin demonstrated that the CP antigens were partly dissociated from, but restricted to, the lamina densa. Western blot analysis showed no differences in molecular weight between the CP antigens and bullous pemphigoid (BP) antigens. CP antigens, as detected by this patient's serum, appear to be constituted of molecules quite similar to BP antigens, but with different epitopes. CP antigens may be shed from basal cells and locate in the area of anchoring filaments, where they play a role in connecting basal cells to the underlying lamina densa.