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This study assessed complement pathways in cystic fibrosis patients, finding no complement deficiency. While Factor B activated more readily in patients, it did not lead to increased complement component consumption.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Cystic fibrosis (CF) is a genetic disorder affecting multiple organs.
- The complement system plays a crucial role in innate immunity.
- Dysregulation of the complement system may contribute to CF pathogenesis.
Purpose of the Study:
- To quantitatively and functionally assess the classical and alternative complement pathways in cystic fibrosis patients.
- To determine if complement deficiencies exist in cystic fibrosis.
- To investigate the activation patterns of complement components, specifically Factor B.
Main Methods:
- Sera from 23 cystic fibrosis patients and controls were analyzed.
- Classical pathway function was measured by CH50 titre.
- Alternative pathway function was assessed by inulin-initiated Factor B cleavage, C3 cleavage, and terminal component consumption.
Main Results:
- Classical complement pathway function was similar in cystic fibrosis patients and controls.
- Alternative pathway function, measured by Factor B cleavage and C3 consumption, was comparable between patients and controls.
- Factor B showed increased activation in cystic fibrosis patient sera, but this did not result in accelerated or more extensive terminal complement component activation.
Conclusions:
- No overall complement deficiency was identified in the studied cystic fibrosis patients.
- The significance of the readily activated Factor B in cystic fibrosis remains undetermined.
- Complement system function appears largely intact in cystic fibrosis despite altered Factor B activation.
Abstract:
Quantitative and functional assessments were made of both the classical and alternative pathways of complement activation in sera from 23 patients with cystic fibrosis. The classical pathway functioned similarly in patients and controls as measured by CH50 titre. Alternative pathway function, initiated in patient sera by incubation with inulin, was equal to that of controls as determined by cleavage of Factor B and C3, and by the consumption of terminal components. Factor B, however, was more readily activated in patient than in control sera. This rapid alteration of Factor B did not lead to accelerated or more extensive activation of the terminal complement components via the alternative pathway when assessed by C3 cleavage and the consumption of terminal components. Thus, a complement deficiency was not found. The importance of the easily activated Factor B is undefined.