Alterations of basement membrane zone in autoimmune subepidermal bullous diseases

Pemphigoid (BP), mucous membrane pemphigoid (MMP) and epidermolysis bullosa acquisita (EBA) are characterized by the presence of in vivo bound and circulating anti-basement membrane zone (BMZ) antibodies directed against different antigens localized in the upper part of the lamina lucida, lamina lucida-lamina densa border and in sublamina densa region, respectively. The alterations of BMZ lead to blister formation.

The aim of the present study was to compare the alterations of various regions of the BMZ in BP, MMP and EBA using laser scanning confocal microscopy (LSCM).

Biopsy specimens taken from perilesional patients' skin were cut into 40mum thick slides, followed by double immunofluorescence labeling with antibodies against different BMZ structures and anti-human IgG antibody. Three-dimensional reconstruction (3DR) of various regions of BMZ and of in vivo bound IgG was performed by computer program integrated with LSCM.

In BP and MMP, LSCM studies revealed numerous invaginations of BMZ, most pronounced at the level of lamina lucida. Integrity of BMZ was preserved at the level of lamina lucida, lamina densa and sublamina densa. In EBA, continuity of lamina lucida was preserved and numerous invaginations were present. More pronounced invaginations of BMZ were observed at the level of lamina densa, whereas at the level of the sublamina densa region the staining along BMZ was discontinuous. Moreover, large clumps composed of collagen VII vertically oriented to the dermal-epidermal junction extending into the mid dermis were observed.

The study showed that alterations of BMZ in BP and MMP occur mainly in the lamina lucida, and in EBA in the sublamina densa region. These alterations in various regions of BMZ in BP, MMP and EBA could be responsible for the differences in the level of blister formation and in the clinical course of the diseases.