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Monoclonal rheumatoid factor-IgG immune complexes. Poor fixation of opsonic C4 and C3 despite efficient complement
Y C Ng1, D K Peters, M J Walport
1Rheumatology Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Arthritis and Rheumatism
|January 1, 1988
Summary
Monoclonal IgM rheumatoid factor-IgG complexes in essential mixed cryoglobulinemia poorly fix complement components C3 and C4. This impairs their clearance by erythrocyte complement receptor type 1 (CR1), potentially contributing to disease pathology.
Area of Science:
- Immunology
- Complement System Biology
- Rheumatology
Background:
- Essential mixed cryoglobulinemia involves monoclonal IgM rheumatoid factor complexing with IgG.
- Rheumatoid factor-IgG complexes are implicated in the pathogenesis of cryoglobulinemia.
Purpose of the Study:
- To investigate the complement-fixing properties of monoclonal IgM rheumatoid factor-IgG complexes.
- To assess the interaction of these complexes with erythrocyte complement receptor type 1 (CR1) and their in vivo clearance.
Main Methods:
- Analysis of C3 and C4 fixation by IgM-IgG complexes.
- In vitro binding assays with normal erythrocytes and CR1.
- In vivo detection of complexes on erythrocytes from patients.
Main Results:
- Monoclonal IgM-IgG complexes exhibit poor C3 and C4 fixation despite efficient fluid-phase C3 conversion.
- Small amounts of C4 fixation may hinder subsequent C3 fixation.
- These complexes demonstrate inefficient binding to erythrocyte CR1 in vitro and are not detected on patient erythrocytes in vivo.
Conclusions:
- The inefficient complement fixation and CR1 binding of these complexes suggest impaired clearance mechanisms.
- Inefficient clearance of these phlogistic complexes may contribute to the pathophysiology of essential mixed cryoglobulinemia.