Goodpasture's disease: molecular architecture of the autoantigen provides clues to etiology and pathogenesis

Purpose of review Goodpasture's disease is an autoimmune disorder characterized by the deposition of pathogenic autoantibodies in basement membranes of kidney and lung, which induces rapidly progressive glomerulonephritis and pulmonary hemorrhage. The target antigen is the alpha 3NC1 domain of collagen IV, which is expressed in target organs as an alpha 345 network. Recent studies of specificity and epitopes of Goodpasture's autoantibodies and discovery of novel posttranslational modification of the antigen, a sulfilimine bond, provide further insight into mechanisms of initiation and progression of Goodpasture's disease. Recent findings Analysis of the specificity of Goodpasture's autoantibodies revealed a distinct subset of circulating and kidney-bound anti alpha 5NC1 antibody, which is associated with loss of kidney function. Structural integrity of the alpha 345NC1 hexamer is stabilized by the novel sulfilimine crosslinks conferring immune privilege to the Goodpasture's autoantigen. Native antibodies may contribute to establishment of immune tolerance to autoantigen. Structural analysis of epitopes for autoantibodies and alloantibodies indicates a critical role of conformational change in the alpha 345NC1 hexamer in eliciting an autoimmune response in Goodpasture's disease. Summary Understanding of the quaternary structure of the Goodpasture's autoantigen continues to provide insights into autoimmune mechanisms that serve as a basis for development of novel diagnostic tools and therapies for Goodpasture's disease.