0000000000009105
AUTHOR
Ursula Antes
Evidence for the presence of autoantibodies to the collagen-like portion of C1q in systemic lupus erythematosus.
We investigated the connection between the C1q solid-phase binding assay (C1q SPBA) and double-stranded DNA antibodies, and analyzed the immune complex material in systemic lupus erythematosus (SLE) sera. Comparison with a new monoclonal assay for C1q-bearing immune complexes (the 242G3 assay) revealed that the immune complexes in SLE bind specifically to solid-phase C1q, and not to fluid-phase C1q. The C1q solid-phase binding activity sedimented as 7S IgG, was insensitive to DNase treatment, and could be selectively absorbed by C1q-coupled beads and by bovine serum albumin-anti-bovine serum albumin C1q beads, but not by DNA. Thus, antibodies to double-stranded DNA do not interfere in the C…
C1q-bearing immune complexes detected by a monoclonal antibody to human C1q in rheumatoid arthritis sera and synovial fluids
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 …
Autoantikörper gegen die Komplementkomponente C1q beim Systemischen Lupus Erythematodes
Autoantibodies against C1q, a subcomponent of the first complement component C1, could be detected in 49.4% of sera from patients with systemic lupus erythematosus (SLE). They are directed against the collagen-like portion of the C1q molecule and recognize only bound, but not fluid-phase C1q. The appearance of these autoantibodies in the course of SLE correlates with the detection of IgG in the C1q-Solid-Phase-Bindingassay, with high titres of dsDNA-antibodies and with depressed total complement activity (CH50) and C1q-values. Our investigations show that autoantibodies against the collagen-like portion of bound C1q but not immune complexes are the main constituent of C1q-binding IgG in SLE.