The location of binding sites of pemphigus vulgaris and pemphigus foliaceus autoantibodies: a post-embedding immunoelectron microscopic study
Pemphigus is a life-threatening autoimmune blistering disease of skin and mucous membranes that has two major subtypes based on clinical and histological features, pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Autoantibodies against the PV antigen (desmoglein 3) and the PF antigen (desmoglein 1) are involved in the pathogenesis of blister formation. In the present study, the location of epitopes recognized by autoantibodies of patients with PV and PF was studied by postembedding immunogold electron microscopy. PV and PF autoantibodies were observed bound predominantly to the intercellular domains of desmosomes, but not to the non-desmosomal keratinocyte cell surface. The relationship between the location of PF antigen and other constitutive desmosomal proteins, desmocollin, desmoplakin and plakoglobin, in normal human skin was investigated using a double immunogold labelling technique. It was observed that PF antigen and desmocollin co-localize within the intercellular domain of the desmosomes. In contrast, the antibodies against desmoplakin and plakoglobin bound predominantly to the intracellular desmosomal attachment plaque with the binding site of the antibody against plakoglobin closer to the desmosomal cell membrane than that of the antibody to desmoplakin. We show that the LR White postembedded immunogold electronmicroscopy technique is convenient and easily applied to studies of autoimmune bullous skin diseases. We have used it to demonstrate the precise localization of the binding sites of PV and PF autoantibodies and their relationship with other constitutive desmosomal proteins.