Antiglomerular basement membrane antibodies in human sera: detection by a modified micro-ELISA

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)

Routine and rapid enzyme linked immunosorbent assays for circulating anti-glomerular basement membrane antibodies

Microtitre plate modifications of the original tube enzyme linked immunosorbent assay (ELISA) of Wheeler and Sussman were used for the routine and rapid assays of anti-glomerular basement membrane antibodies in human sera. In a prospective study of 238 sera from 200 patients, the routine assay (about 24 hours) detected circulating antibodies in seven sera from three patients with active anti-glomerular basement membrane disease. The remaining sera, from patients with a variety of other glomerulonephropathies, were negative by the assay. The rapid assays took less than four hours, and in a retrospective study, detected anti-glomerular basement membrane antibodies in a range of 15 positive sera, with a level of discrimination similar to that observed in the routine assay and with no false positive/negative results.

Anti-glomerular basement membrane antibody-mediated glomerulonephritis due to glue sniffing

A 16-year-old girl developed rapidly progressive glomerulonephritis and renal failure. The disease was associated with high titres of antiglomerular basement membrane antibodies in serum, linear deposits of immunoglobulin G and diffuse epithelial crescents on renal biopsy. Past history revealed heavy smoking and deliberate sniffing of Pattex glue, a mixture of hydrocarbons which possibly may affect the structure of glomerular basement membrane. After treatment by repeated plasmapheresis and drug immunosuppression autoantibodies disappeared from serum but renal function was not influenced. Renal damage is a potential hazard for glue sniffing adolescents.