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Studies of C1 subcomponents in chronic urticaria and angioedema
Insights
Complement component abnormalities are common in patients with chronic urticaria and angioedema, but not due to genetic deficiencies. These findings suggest acquired complement system dysregulation in these conditions.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Chronic urticaria and angioedema are common conditions.
- The complement system plays a crucial role in immune responses and inflammation.
- Alterations in complement components may be associated with these conditions.
Purpose of the Study:
- To investigate the levels and integrity of complement components C1q, C1r, C1s, C3, C4, and C-1 inhibitor (C-1 IA) in patients with chronic urticaria or angioedema.
- To identify potential complement system dysregulation in these patient cohorts.
Main Methods:
- Electroimmunoassay was used to quantify C1q, C1r, C1s, C3, C4, and C-1 IA levels in 150 patients.
- Crossed immunoelectrophoresis was employed to detect abnormal C1 subcomponent complexes.
- Hemolytic and esterolytic assays were performed to assess C1 activity.
Main Results:
- Approximately 30% of patients exhibited abnormal levels of C1q and C1s.
- Seven patients had unmeasurable C1r levels due to precipitates.
- Decreased C3 and/or C4 levels were observed in five patients with C1 subcomponent aberrations.
- C1r-C1s complexes were found in 11% of patients, and alpha2 complexes (C-1r-C-1-S-C-1 IA) in 33%.
- Low C1 activity was detected in sera with decreased C1q levels or abnormal C1r precipitates.
- No evidence of genetically determined deficiencies in C1q, C1r, or C-1 IA was found.
Conclusions:
- Acquired abnormalities in complement components, particularly C1 subcomponents, are frequent in patients with chronic urticaria and angioedema.
- The observed complement dysregulation appears to be acquired rather than genetically determined.
- These findings highlight the potential involvement of acquired complement system dysregulation in the pathogenesis of chronic urticaria and angioedema.
Abstract:
C1q, C1r, C1s, C3, C4 and C-1 IA were determined by electroimmunoassay in sera from 150 patients with chronic urticaria or angioedema. Abnormal C1q and C1s levels were found in about 30% of the patients. In seven sera C1r was not measurable due to the appearance of diffuse precipitates. The levels of C3 and/or C4 were decreased in five sera with aberrations of C1 subcomponents in the electroimmunoassay. None of the patients showed reduced C-1 IA levels in the electroimmunoassay. The presence in sera of abnormal C1 subcomponent complexes was studied by crossed immunoelectrophoresis. Sera from 11% of the patients contained C1r-C1s complexes. Increased amounts of alpha2 complexes (C-1r-C-1-S-C-1 IA) were found in 33% of the patients. A major part of the C1q in sera yielding abnormal C1r precipitates had the same electrophoretic mobility as isolated C1q and was not associated with the C1qrs complex. C1 activity in hemolytic tests was low in these sera as well as in sera with decreased C1q levels. In the esterolytic assay for C-1 IA low values were found in 14 patients. Repeated sampling and family studies in appropriate cases gave no evidence for genetically determined deficiencies of C1q, C1r or C-1 IA.