IgG, IgA and IgE autoantibodies against the ectodomain of BP180 in patients with bullous and cicatricial pemphigoid and linear IgA bullous dermatosis

Background Bullous pemphigoid (BP), linear IgA bullous dermatosis (LABD) an d cicatricial pemphigoid (CP) are clinically distinct autoimmune bullous sk in diseases characterized by autoantibodies against components of the epide rmal basement membrane. Like most patients with BP, a significant subgroup of patients with CP has circulating IgG specific for BP180, a transmembrane ous protein of hemidesmosomes. Moreover, sera of patients with LABD contain IgA autoantibodies reactive with a 97/120-kDa protein, LABD antigen 1, whi ch is highly homologous to the extracellular portion of BP180. Objectives We aimed to determine whether, in these diseases, autoantibody r eactivity to BP180 is restricted to distinct immunoglobulin subtypes. Methods Utilizing a baculovirus-encoded form of the ectodomain of BP180, se ra from patients with BP (n = 10), CP (n = 9), LABD (n = 10) and normal hum an control sera (n = 10) were analysed by immunoblot for IgG, IgA and IgE r eactivity against BP180. Results All of 10 BP sera displayed IgG, IgA and IgE reactivity with BP180. Six and seven of nine CP sera, respectively, contained IgG and IgA autoant ibodies reactive with BP180, but none of nine sera contained BP180-specific IgE, Nine of 10 LABD sera contained IgA, and six of 10 IgG, which was reac tive with BP180, but none of 10 sera showed IgE reactivity to BP180. Conclusions The presence of IgG and IgA autoantibody responses to BP180 in patients with three clinically distinct autoimmune bullous diseases indicat es that an autoimmune response to the same distinct adhesion protein may le ad to different clinical manifestations. It is therefore conceivable that v ariable epitopes of BP180 are targeted by the different autoantibody isotyp es, resulting in the distinct clinical pictures.