Subepidermal autoimmune blistering
dermatoses (AIBD) are prototypic
autoantibody-mediated diseases. In
epidermolysis bullosa acquisita (EBA), an
autoimmune disease with severe and chronic skin blistering,
autoantibodies are directed against
type VII collagen.
IgG is the predominant
autoantibody isotype of EBA, the pathogenicity of which has been demonstrated in a variety of in vivo and ex vivo disease models. In contrast, there is not much evidence for the pathogenicity of
IgA, which may appear as the only
autoantibody isotype in some EBA patients. To investigate the pathogenic potential of
IgA autoantibodies, we generated chimeric V gene-matched human
IgA1,
IgA2, and control
IgG1 autoantibodies directed against
type VII collagen. Immobilized
immune complexes containing the rIgA1 and rIgA2
autoantibodies induced the dose-dependent release of
reactive oxygen species from neutrophil granulocytes, a precondition for
blister formation. Moreover, both rIgA1 and rIgA2 induced leukocyte-dependent dermal-epidermal separation in cryosections of human skin. In contrast with rIgG1, neither rIgA1 nor rIgA2 was capable of inducing
complement deposition at the dermal-epidermal junction. Because complement activation is a prerequisite for
blister induction, this lack of function compared with
IgG1 may be compensated for by the stronger activation of neutrophil granulocytes by both
IgA1 and
IgA2. For
IgG-mediated AIBD, immunoadsorption
therapy is a convenient treatment modality for the removal of pathogenic
autoantibodies, particularly in treatment-resistant cases. The results of this study show the pathogenic potential of
IgA autoantibodies and support the development of adsorber matrices for
IgA-mediated AIBD.