Different immunologic properties of the globular NC1 domain of collagen type IV isolated from various human basement membranes.
The C-terminal globular domain NC1 of collagen IV, which carries the epitopes recognized by anti-GBM antibodies in Goodpasture's syndrome, was isolated from human basement membranes (BM) of glomeruli (GBM-NC1), tubules (TBM-NC1), lung (ABM-NC1), placenta (PBM-NC1), and small intestine (IBM-NC1). All NC1 hexamers were of globular size on electron microscopy. On SDS-PAGE, the hexamers dissociated into monomeric and dimer-sized subunits of similar molecular weights. The following monomer:dimer relationships were identified: GBM-NC1, and PBM-NC1 = 1:3; ABM-NC1 = 1:4; and IBM-NC1 = 1:32. On immunoblot, all dimers of the various NC1 globules showed binding of anti-GBM antibodies. However, monomers stained differently, with three monomers demonstrable in GBM-NC1 and no monomer staining in PBM-NC1. In addition, studies with monoclonal antibodies showed that the C-terminus of the alpha 1(IV) collagen chain was demonstrable in all different NC1 hexamers. In contrast, the alpha 3(IV) chain, to which Goodpasture sera preferentially bind, showed a restricted distribution. One monomer and dimers were demonstrable in GBM-NC1 and ABM-NC1, only a weak dimer staining was seen in TBM-NC1, while no evidence for alpha 3(IV) was found in IBM-NC1 and PBM-NC1. Dissociation by 6 M guanidine-HC1 or treatment by acid increases the apparent number of accessible epitopes for anti-GBM antibodies. In addition, dose-response curves, which were obtained by incubation of increasing concentrations of NC1 with anti-GBM antibody positive sera, indicated that for GBM-NC1 and ABM-NC1 the lowest NC1 protein concentrations were necessary to bind 50% of the antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)
Weber
M
M
4th Department of Internal Medicine, University of Erlangen-Nürnberg, Germany.
Pullig
O
O
D019867:Anti-Glomerular Basement Membrane Disease / Q000276:immunology; D001485:Basement Membrane / Q000737:chemistry / Q000276:immunology*; D003094:Collagen / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D000939:Epitopes / Q000737:chemistry / Q000302:isolation & purification; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000737:chemistry / Q000276:immunology; D007678:Kidney Glomerulus / Q000737:chemistry / Q000276:immunology; D007684:Kidney Tubules / Q000737:chemistry / Q000276:immunology; D010920:Placenta / Q000737:chemistry / Q000276:immunology; D011247:Pregnancy; D011487:Protein Conformation; D011650:Pulmonary Alveoli / Q000737:chemistry / Q000276:immunology
D000939:Epitopes; D003094:Collagen