[Study of epitopic sites of the major bullous pemphigoid antigen (BPAg1)]

Bullous pemphigoid is an acquired blistering skin disease associated with the production of IgG autoantibodies to 230 kDa BP Ag (BPAg1) and to 180 kDa BP Ag (BPAg2). The aim of our work was to better characterize the epitopes of BPAg1. For this, we firstly generated a bullous pemphigoid recombinant protein of 55 kDa Mr (rBP55) from a cDNA sequence encoding for the carboxyterminal region of the 230 kDa BP antigen. Ninety-two percent of sera from patients with autoantibodies to the 230 kDa polypeptide recognized the rBP 55 protein. These results confirm that this 555 aminoacid segment corresponding to rBP 55 contains major epitopes. In order to study the epitopes of the amino-terminal portion of the BPAg1 antigen, we generated immortalized B cell lines secreting human monoclonal antibodies to BPAg1 from two patients whose sera reacted with native BPAg1 but not with the recombinant rBP55 carboxy-terminal peptide. Blocking immunofluorescence experiments and phylogenetic studies showed that these human monoclonal antibodies recognize different epitopes of BPAg1. According to these studies, we can conclude on the wide variety of epitopes recognized by BPAg1 autoantibodies.