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Complement-activating properties of IgM rheumatoid factors reacting with IgG subclasses
1Department of Internal Medicine II, Fukushima Medical College, Japan.
Clinical Rheumatology
|July 1, 1995
Summary
IgM rheumatoid factor (RF) reacting with IgG3 significantly activates complement more than other IgG subclasses. This suggests IgG3-bound IgM RF may drive greater inflammation in rheumatoid arthritis synovium.
Area of Science:
- Immunology
- Rheumatology
- Complement System
Background:
- Rheumatoid arthritis (RA) involves chronic inflammation in the synovium.
- IgM rheumatoid factor (RF) and IgG subclasses are implicated in RA pathogenesis.
- The complement-activating property (CAP) of IgM RF with different IgG subclasses is not fully understood.
Purpose of the Study:
- To quantify the complement-activating property (CAP) of IgM RF against various IgG subclasses.
- To investigate the role of IgM RF-IgG subclass interactions in complement-mediated inflammation in RA.
Main Methods:
- Purification of IgM RF from rheumatoid arthritis synovial fluids.
- Enzyme-linked immunosorbent assay (ELISA) to measure C4 activation and binding.
- Utilized biotinylated F(ab')2 antibody to human C4 for detection.
Main Results:
- IgM RF demonstrated significantly higher CAP when reacting with IgG3 compared to other IgG subclasses (P < 0.01).
- This indicates a preferential activation of the classical complement pathway by IgM RF-IgG3 complexes.
Conclusions:
- IgM RF interacting with IgG3 exhibits a potent complement-activating property.
- IgM RF bound to IgG3 may contribute more significantly to complement-dependent inflammation in the RA synovium than IgM RF bound to other IgG subclasses.