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Cystic fibrosis patients show decreased complement components C3 and C4, unlike previous findings. Pseudomonas aeruginosa infection is linked to these complement defects, suggesting pulmonary infection as the likely cause.
Area of Science:
- Immunology
- Pulmonology
- Biochemistry
Background:
- Cystic fibrosis (CF) is a genetic disorder affecting multiple organs, including the lungs.
- The role of complement system activation in CF pathogenesis is not fully understood.
- Previous studies have yielded conflicting results regarding complement levels in CF patients.
Purpose of the Study:
- To investigate complement component levels (C3, C4, C3A) in cystic fibrosis patients.
- To explore the relationship between complement levels, clinical scores, sputum microbiology, and patient sex.
- To determine the potential involvement of complement activation pathways in CF.
Main Methods:
- Quantification of complement components C3, C4, and C3A in 30 CF patients (ages 1-21) and 40 healthy controls.
- Correlation analysis with Shwachman clinical scores, sputum microbiology (including Pseudomonas aeruginosa), and patient sex.
- Assessment of alternative pathway activation.
Main Results:
- Significant reductions in C3 (P < 0.001) and C4 (P < 0.02) were observed in CF patients compared to controls.
- C3A levels remained unaltered; no complement component increases were detected.
- Pseudomonas aeruginosa in sputum was associated with complement defects (14/18 patients).
- Alternative pathway activation was detected in 32% of patients.
- Clinical scores, disease exacerbations, and patient sex did not influence complement levels.
Conclusions:
- The study demonstrates decreased C3 and C4 levels in CF patients, contrary to some prior reports.
- Pulmonary infection, particularly with Pseudomonas aeruginosa, is strongly implicated in complement activation and subsequent defects in CF.
- Observed complement defects are likely secondary to chronic pulmonary inflammation and infection.
Abstract:
Complement components C3, C4, and C3A were estimated in 30 patients with cystic fibrosis aged 1 to 21 years (M:F = 16:14) and were compared with results in 40 healthy, age-matched subjects. The influences of the clinical score, sputum microbiology, and the patients' sex were also investigated. In contrast to most previous communications, this paper shows that, compared to the control group, a significant decrease of C3 (P less than 0.001) and C4 (P less than 0.02) was observed whereas C3A levels were not altered. There were no increases in complement. Shwachman-scores above or below 70 did not influence the complement levels, nor did exacerbations of the disease change the levels. No influence of the patients' sex could be shown. Pseudomonas aer. in the sputum was clearly associated with complement defects (14/18). Alternative-pathway involvement of complement activation could be demonstrated in 32%. The results make complement activation due to pulmonary infection most likely. The defects observed probably represent secondary changes.