C1q-bearing immune complexes detected by a monoclonal antibody to human C1q in rheumatoid arthritis sera and synovial fluids

U. Antes, H. P. Heinz, D. Schultz, D. Brackertz, M. Loos

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Using a monoclonal antibody directed against the C-chain of human C1q, we detected C1q-bearing immune complexes (IC) in sera and synovial fluids of rheumatoid arthritis (RA) patients. In a sandwich-ELISA, C1q-bearing IC were captured by the solid-phase monoclonal antibody and then detected with peroxidase-labeled F(ab′)2-antibodies to either human IgG or IgM. The results of this assay were compared to an ELISA-modification of the C1q-solid-phase binding assay (C1q-SPBA). C1q-bearing IC were detected in 81.1% of RA-sera and the 65.2% of RA-synovial fluids. IgG as well as IgM was present in 72.6% of the sera and 70% of the synovial fluids which were positive in both assays. Most RA sera that were only positive for C1q-bearing IC, contained IgG alone (81.5%). The corresponding synovial fluids showed IgG alone (53%) or both IgG and IgM (41.1%). IgM alone (25%) could be detected in sera, e.g. in juvenile forms of RA. The levels of IC were higher in synovial fluid than in paired serum. In comparison to normal human serum (NHS) and patients with osteoarthritis, complement activity (CH50 titers) and C1q-values in patients with RA were frequently elevated. Since the formation of C1q-bearing IC is an indicator for the classical complement pathway activation, an assay with monoclonal anti-C1q antibody may be a useful tool in the diagnosis of rheumatoid diseases.

Original languageEnglish (US)
Pages (from-to)245-250
Number of pages6
JournalRheumatology International
Volume10
Issue number6
DOIs
StatePublished - Nov 1 1991

Keywords

  • C1q-bearing immune complexes
  • Immune complexes
  • Monoclonal anti-C1q antibody
  • Rheumatoid arthritis sera/synovial fluids

ASJC Scopus subject areas

  • Rheumatology

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