New insights into the autoantibody-mediated mechanisms of autoimmune bullous diseases and urticaria.

The skin is a common target of cellular and/or antibody mediated pathological immune responses. Pemphigoids, pemphigus vulgaris and dermatitis herpetiformis are bullous disease due to autoantibodies targeting specific proteins of the skin. The pemphigoid autoantigens are the BP180 and the BP230 antigens, two components of the epithelial basement membrane zone. Additional antigenic targets reported in a portion of patients are laminin 5, the alpha6 subunit of the hemidesmosomal integrin alpha6beta4 and a glycoprotein termed p200. The epidermal and mucosal epithelial cells detachment (acantholysis) characteristic of pemphigus vulgaris is induced by autoantibodies directed against the desmoglein 3 and 1. The desmogleins are desmosomal cadherins, which play a major role in the cell-to-cell adhesion. Dermatitis herpetiformis is regarded as cutaneous phenotype of coeliac disease. A novel autoimmune hypothesis of coeliac disease links wheat gliadin and tissue transglutaminase (TG2) in the gut, which leads to T cell response and IgA autoantibody formation. In dermatitis herpetiformis skin the target for IgA deposition seems to be epidermal TG3. Urticaria is a complex syndrome caused by both immune and non-immune mechanisms. In a subsets of patients with chronic urticaria mast cell degranulation is induced by autoantibodies directed against the a-subunit of the high-affinity IgE receptor, and/or the IgE.