title: Antibodies against C1q in anti-glomerular basement membrane nephritis.
abstract: The prevalence of antibodies against the collagen-like region of the subcomponent of the first component of complement, C1q, was investigated in 11 patients with anti-glomerular basement membrane (GBM) nephritis. Anti-C1q antibodies (anti-C1qAb) were detected in seven patients. IgG anti-C1qAb were found in four and IgA anti-C1qAb in five patients. During follow up of the patients a relationship was observed between the levels of IgG anti-C1qAb and the levels of anti-GBM antibodies (anti-GBMAb). Gelfiltration experiments indicated that both IgG anti-C1qAb as well as IgG anti-GBMAb were monomeric and that binding also occurred with the F(ab')2 fragments of the antibodies. Although anti-C1qAb and anti-GBMAb are both directed against a collagen-like structure, it was demonstrated by means of inhibition experiments that anti-C1qAb and anti-GBMAb are directed against different antigenic sites. Comparison of patients with anti-GBM nephritis with and without anti-C1qAb revealed that there were no differences in disease activity or disease severity. Therefore, the results of this study suggest that anti-C1qAb do not play a direct pathogenetic role in anti-GBM nephritis.
authors.affiliation: Department of Rheumatology, University Hospital, Leiden, The Netherlands.
authors.forename: I E
authors.initials: IE
authors.lastname: Coremans
authors.forename: M R
authors.initials: MR
authors.lastname: Daha
authors.forename: E A
authors.initials: EA
authors.lastname: van der Voort
authors.forename: Y
authors.initials: Y
authors.lastname: Muizert
authors.forename: C
authors.initials: C
authors.lastname: Halma
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000276:immunology*; D001485:Basement Membrane / Q000276:immunology*; D015922:Complement C1q / Q000276:immunology*; D005921:Glomerulonephritis / Q000276:immunology*; D006801:Humans; D007678:Kidney Glomerulus / Q000276:immunology; D008875:Middle Aged
chemical_list: D001323:Autoantibodies; D015922:Complement C1q