Molecular overlap of the IgA target antigens in the subepidermal blistering diseases.

Linear IgA disease (LAD) has circulating IgA auto-antibodies which have been found to be associated with epidermal- and dermal-derived antigens. The localization and molecular weight(s) of the IgA target antigen(s) implicated in LAD and their relationship to the target antigens for the IgA antibodies in bullous pemphigoid (BP) and cicatricial pemphigoid (CP) are unknown. Sera from patients with all 3 diseases who had circulating IgA antibodies were studied by immunoblotting with both epidermal and dermal extracts. Our findings indicate that there is heterogeneity in the localization and molecular weights of the target antigen(s), with multiple bands demonstrated with some sera. Three principal target antigens were identified with molecular weights of 110-120, 160-180 and one approximately 285 kD. These antigens were common to all 3 diseases and were found in 25 patients. These results suggest that the target antigens for IgA basement membrane zone antibodies in LAD, BP and CP are multiple, complex in composition and may differ from the conventional BP antigens.