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C1 subcomponent complexes and C2 cleavage in active systemic lupus erythematosus.
H Jonsson1, A G Sjöholm, U Mårtensson
1Department of Rheumatology, University Hospital, Lund, Sweden.
Complement and Inflammation
|January 1, 1991
Summary
In active systemic lupus erythematosus (SLE), C1 dissociation and C1 inactivator (C1 IA)-containing complexes are common, suggesting C1 IA
Area of Science:
- Immunology
- Rheumatology
Background:
- Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune complex deposition and inflammation.
- The classical complement pathway plays a role in SLE pathogenesis.
- C1 inactivator (C1 IA) regulates the classical complement pathway.
Purpose of the Study:
- To investigate the activation and C1 IA-dependent dissociation of the C1 complex.
- To correlate these events with classical pathway recruitment in SLE patients during disease flares.
- To assess the relationship between complement activation and SLE clinical severity.
Main Methods:
- Studied 24 SLE patients divided into three clinical groups based on disease activity (mild, major extrarenal, renal).
- Analyzed serum concentrations of C1 IA-C1r-C1s and C1 IA-C1r-C1s-C1 IA complexes.
- Assessed C2 and C3 cleavage in EDTA plasma to indicate classical pathway activation.
Main Results:
- High concentrations of C1 IA-C1r-C1s trimers were found in most SLE patients.
- Some patients with high trimers showed no classical pathway activation, indicating C1 IA control at the C1r level.
- Formation of C1 IA-C1r-C1s-C1 IA tetramers correlated with C2/C3 cleavage and hypocomplementemia.
- Classical pathway recruitment was linked to SLE disease severity.
Conclusions:
- C1 dissociation with C1 IA-containing complexes is consistently observed in active SLE.
- C1 IA-dependent control of C1 activation is biologically significant in SLE.
- C1 IA-C1r-C1s-C1 IA tetramers may not always be a sensitive indicator of classical pathway activation.