 In the immunologic component, autoantibodies act against the hemidesmosomal bullous pemphigoid antigens BP230 (BPAg1) and BP 180(BPAg2 or type XVII collagen) which are located at the lamina lucida of the basement membrane zone.These antigens play an important role in the adhesion complexes that promote epithelial-stromal adhesion.The predominant subclass of antibodies that acts against the antigens is IgG4.