title: Distinct epitopes for anti-glomerular basement membrane alport alloantibodies and goodpasture autoantibodies within the noncollagenous domain of alpha3(IV) collagen: a janus-faced antigen.
abstract: Alport posttransplantation anti-glomerular basement membrane (GBM) nephritis is mediated by alloantibodies against the noncollagenous (NC1) domains of the alpha3alpha4alpha5(IV) collagen network, which is present in the GBM of the allograft but absent from Alport kidneys. The specificity of kidney-bound anti-GBM alloantibodies from a patient who had autosomal recessive Alport syndrome (ARAS) and developed posttransplantation nephritis was compared with that of Goodpasture autoantibodies from patients with autoimmune anti-GBM disease. Allograft-eluted alloantibodies reacted specifically with alpha3alpha4alpha5 NC1 hexamers, targeting their alpha3NC1 and alpha4NC1 subunits, and recognized a noncontiguous alloepitope formed jointly by the E(A) and E(B) regions of alpha3NC1 domain. In contrast, human Goodpasture autoantibodies recognized the separate E(A) and E(B) autoepitopes of alpha3NC1 but not the composite alloepitope. Molecular modeling of alpha3NC1 revealed that the alloepitope is more accessible within the NC1 hexamers than the partially sequestered Goodpasture autoepitopes. Overall, the specificity of alloantibodies indicated a selective lack of immune tolerance toward the alpha3 and alpha4(IV) collagen chains not expressed in patients with ARAS. Using COL4A3 knockout mice, a model of ARAS, it was shown further that acid-dissociated rather than native alpha3alpha4alpha5 NC1 hexamers elicited murine anti-GBM antibodies most closely resembling human ARAS alloantibodies. In contrast, alpha3NC1 monomers elicited Goodpasture-like murine antibodies, targeting the E(A) and E(B) autoepitopes. Thus, the identity of alpha3NC1 epitopes targeted by anti-GBM antibodies is strongly influenced by the molecular organization of the immunogen. These findings suggest that different isoforms of alpha3(IV) collagen may be implicated in the pathogenesis of ARAS posttransplantation anti-GBM nephritis and Goodpasture disease.
authors.affiliation: Division of Nephrology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
authors.forename: Xu-Ping
authors.initials: XP
authors.lastname: Wang
authors.forename: Agnes B
authors.initials: AB
authors.lastname: Fogo
authors.forename: Selene
authors.initials: S
authors.lastname: Colon
authors.forename: Giovanna
authors.initials: G
authors.lastname: Giannico
authors.forename: Sameh R
authors.initials: SR
authors.lastname: Abul-Ezz
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Miner
authors.forename: Dorin-Bogdan
authors.initials: DB
authors.lastname: Borza
mesh_terms: D000328:Adult; D019867:Anti-Glomerular Basement Membrane Disease / Q000175:diagnosis* / Q000276:immunology*; D000906:Antibodies / Q000276:immunology*; D001323:Autoantibodies; D001707:Biopsy, Needle; D003094:Collagen / Q000276:immunology; D024141:Collagen Type IV / Q000276:immunology; D018450:Disease Progression; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D017809:Fatal Outcome; D005260:Female; D006084:Graft Rejection; D006801:Humans; D007150:Immunohistochemistry; D007518:Isoantibodies / Q000276:immunology*; D007676:Kidney Failure, Chronic / Q000209:etiology / Q000473:pathology / Q000601:surgery*; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000276:immunology; D009394:Nephritis, Hereditary / Q000150:complications / Q000175:diagnosis; D018570:Risk Assessment; D014181:Transplantation Immunology / Q000502:physiology
chemical_list: D000906:Antibodies; D001323:Autoantibodies; D024141:Collagen Type IV; D000939:Epitopes; D007518:Isoantibodies; C051951:antiglomerular basement membrane antibody; D003094:Collagen