Epidermolysis bullosa acquisita (EBA) is an autoimmune sub-epidermal blistering disease characterized by autoantibodies to type VII (anchoring fibril) collagen. To date, however, direct evidence for a pathogenic role of human EBA autoantibodies has not been demonstrated. In this study, we affinity-purified anti-type VII collagen antibodies from EBA patients' sera and then injected them into adult hairless immunocompetent mice. Mice injected with EBA autoantibodies developed skin fragility, blisters, erosions, and nail loss on their paws - all features of EBA patients. By clinical, histological, immunological, and ultrastructural parameters, the induced lesions were reminiscent of human EBA. Histology showed bullous lesions with an epidermal-dermal separation. IgG and C3 deposits were observed at the epidermal-dermal junction. All mice had serum antibodies that labeled the dermal side of salt-split human skin like EBA sera. Direct immunogold electron microscopy specifically localized deposits of human IgG to anchoring fibrils. (Fab')(2) fragments generated from EBA autoantibodies did not induce disease. We conclude that EBA human patient autoantibodies cause sub-epidermal blisters and induce EBA skin lesions in mice. These passive transfer studies demonstrate that human EBA autoantibodies are pathogenic. This novel EBA mouse model can be used to further investigate EBA autoimmunity and to develop possible therapies.

Epidermolysis bullosa acquisita (EBA) is an acquired bullous disease of the skin characterized by IgG autoantibodies against type VII (anchoring fibril) collagen. We previously defined four immunodominant antigenic epitopes within the noncollagenous 1 (NC1) domain of type VII collagen. In this study, we produced an additional recombinant fusion protein from the NC1 domain corresponding to the N-terminal 227 amino acids (residues 1 to 227), which contains homology with cartilage matrix protein (CMP). Using enzyme-linked immunosorbent assay and immunoblot analysis, we tested sera from EBA patients (n ‫؍‬ 32), bullous systemic lupus erythematosus patients (n ‫؍‬ 3), bullous pemphigoid patients (n ‫؍‬ 15), and normal humans (n ‫؍‬ 12). Twenty-six of 32 EBA sera and two of three bullous systemic lupus erythematosus sera reacted with the CMP domain, whereas none of the control sera did. Affinity-purified anti-CMP EBA antibodies injected into hairless mice produced the clinical, histological, immunological, and ultrastructural features of EBA. F(ab) 2 fragments generated from anti-CMP EBA autoantibodies did not induce disease. Our studies provide the first evidence that EBA autoantibodies to the CMP subdomain of NC1 are pathogenic and induce blister formation. This is the first antigenic epitope on type VII collagen demonstrated to be a pathogenic target for EBA autoantibodies. Epidermolysis bullosa acquisita (EBA) is a severe, chronic, subepidermal bullous disease of the skin and mucosa characterized by skin fragility, blisters in traumaprone sites, scarring with milia formation, and nail dystrophy.1 It is a prototypic autoimmune disease in which EBA patients have in vivo tissue-bound and circulating IgG autoantibodies directed against type VII collagen, a major component of anchoring fibrils, structures that anchor the epidermis onto the dermis.2-8 EBA autoantibodies bind to type VII collagen within anchoring fibrils. EBA patients have a diminution of normal anchoring fibrils and subsequent epidermal-dermal disadherence. The clinical appearance of EBA patients and the histology of their cutaneous lesions are often very reminiscent of hereditary dystrophic epidermolysis bullosa. These two diseases are etiologically unrelated but share the common feature of decreased anchoring fibrils. In the case of inherited dystrophic epidermolysis bullosa, the cause of decreased or absent anchoring fibrils is a genetic defect in the gene that encodes for type VII collagen. 9,10Type VII collagen is composed of three identical ␣ chains, each consisting of a 145-kd central collagenous triple-helical segment characterized by repeating Gly-X-Y amino acid sequences, flanked by a large 145-kd amino-terminal noncollagenous domain (NC1), and a small 34-kd carboxyl-terminal noncollagenous domain (NC2). 6 -8,11,12 Within the extracellular space, type VII collagen molecules form anti-parallel, tail-to-tail dimers stabilized by disulfide bonding through a small carboxylterminal NC2 overlap between two type VII collagen molecules. The anti-para...

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