Linear IgA bullous dermatosis with IgA antibodies exclusively directed against the 180- or 230-kDa epidermal antigens.

This study describes the presence in sera from patients with linear IgA bullous dermatosis (LABD) of IgA antibodies specific for 230- or 180-kDa epidermal antigens. Of 11 patients' sera with IgA antibodies reactive with the epidermal antigens obtained from cultured keratinocytes, 6 sera recognized the 230-kDa antigen and co-migrated with the polypeptide recognized by a human monoclonal antibody against the 230-kDa bullous pemphigoid antigen (BPAgl). Five sera recognized the 180-kDa antigen and co-migrated with the polypeptide stained by a polyclonal antibody to the 180-kDa bullous pemphigoid antigen (BPAg2). None of these LABD sera contained IgG antibodies reactive with the basement membrane zone antigens and none labeled a 97-kDa epidermal antigen or a 290-kDa dermal antigen. Immunoaffinity-purified IgA antibodies from the 230 kDa band further reacted with the epidermal side of the skin basement membrane zone. Epitope mapping with rBP55, a fusion protein containing the C-terminal end of BPAg1, suggested that the major antigenic epitopes for LABD and BP antibodies on the 230-kDa antigen are different. Only one serum with IgA antibodies was found to label rBP55, contrasting with nine of ten BP sera reacting with this protein. Our study demonstrates the presence of an exclusive IgA response against the 230- or 180-kDa antigens in a subset of patients with LABD.