Defining target antigens in linear IgA disease using skin from subjects with inherited epidermolysis bullosa as a substrate for indirect immunofluorescence microscopy

Identification of target antigens in immunobullous disorders usually involv es laborious techniques such as immunoblotting and immunoprecipitation, whi ch do not always provide conclusive data. This is particularly true of line ar IgA disease (LAD) in which the target antigen has often proved difficult to identify, As an alternative means of antigen identification in five adu lt patients with LAD, we performed indirect immunofluorescence (IIF) micros copy on a panel of skin samples taken from subjects with different forms of inherited epidermolysis bullosa (EB), Skin samples were selected that show ed a complete absence of immunostaining for a specific basement membrane zo ne (BMZ) molecule (type VII collagen, laminin 5 or the 180-kDa bullous pemp higoid antigen BP180). In each case, the underlying genetic mutations had b een defined and shown to consist of premature termination codons on both al leles of the particular gene, resulting in total ablation of the encoded pr otein. Two epidermal-binding LAD sera showed BMZ fluorescence on all substr ates except BP180-deficient skin, suggesting that the target antigen was BP 180, or a closely related molecule. In contrast, two dermal-binding LAD ser a were positive on all substrates except the type VII collagen-deficient sl ;in, suggesting that the target antigen was likely to be type VII collagen. One LAD serum sample, which showed combined dermal and epidermal fluoresce nce on normal salt-split skin, was also positive on all substrates tested, suggesting a target antigen other than type VII collagen, laminin 5 or BP18 0, ae study confirms that LAD is a heterogeneous disorder and illustrates t hat IIF using a panel of skin samples which lack specific BMZ molecules, ta ken from subjects with inherited EB, is a relatively simple and useful tool to help identify target antigens in immunobullous disorders.