Autoimmunity in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease primarily of the elderly, characterized by the development of urticarial plaques surmounted by subepidermal blisters and the deposition of immunoglobulins and complement at the basement membrane zone (BMZ). Immunologically, it is characterized by the development of autoantibodies targeting two structural proteins of the hemidesmosomes, BP180 (collagen XVII) and BP230. BP230 is intracellular protein of the hemidesmosomal plaque, while BP180 is a transmembrane protein with a collagenous extracellular domain. The weight of experimental evidence indicates that BP180 is the primary target of the pathogenic autoantibodies. Autoantibodies are of both the IgG or IgE class, and their binding in the skin triggers complement activation, mast cell degranulation and the accumulation of inflammatory cells, including eosinophils, mast cells, and neutrophils. Release of proteases from these inflammatory cells results in cleavage of the BMZ and blister formation. While the initial triggers of autoantibody production remain obscure, a better understanding of the pathomechanisms of blister formation will lead to the development of new therapeutic strategies.