Ultrastructural localization of binding sites of sera from patients with linear IgA bullous dermatosis

The localization of the antigen recognized by IgA basement membrane zone (BMZ) antibodies from patients with linear IgA bullous dermatosis (LABD) has not been established. The aim of our study was to find out the binding sites for IgA-BMZ antibodies in LABD in adults and children and, for comparison, the binding sites for IgA antibodies in IgA cicatricial pemphigoid (IgA-CP). Our series comprised 21 sera from adult LABD, 4 sera from childhood LABD, and 2 sera from IgA-CP. The studies were performed using the sodium chloride split-skin method and indirect immunoelectron microscopy (IEM) with the use of the pre-embedding immunoperoxidase technique on two substrates: monkey oesophagus and normal human skin. Of the 27 sera, 24 reacted with the epidermis (19 from adult, 4 from childhood LABD and 1 from IgA-CP) and at the electron microscopic level labelled the upper part of the lamina lucida (LL) and/or hemidesmosomes, and 2 reacted with the dermis (1 from typical adult LABD and 1 from IgA-CP) and labelled the sublamina densa (SLD) region. Two sera were negative in IEM. In conclusion, the study indicated that the localization of the antigens is similar in adult and childhood LABD, and in IgA-CP.