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Complement activation in pulmonary tuberculosis
K S Sai Baba1, K D Moudgil, R C Jain
1Department of Biochemistry, All India Institute of Medical Sciences, Ansari Nagar.
Insights
Complement levels (CH50, C3, C3d) and immune complexes (CICs) are elevated in untreated tuberculosis patients, correlating with disease severity. Treatment normalizes these markers, suggesting complement plays a role in managing tuberculosis immune responses.
Area of Science:
- Immunology
- Infectious Diseases
- Clinical Chemistry
Background:
- Pulmonary tuberculosis is associated with complex immune dysregulation.
- Complement system activation is implicated in host defense and pathology during infection.
Purpose of the Study:
- To investigate alterations in complement activity (CH50), complement components (C3, C3d), and circulating immune complexes (CICs) in pulmonary tuberculosis.
- To correlate these changes with disease severity and treatment status.
Main Methods:
- Serum/plasma samples from untreated tuberculosis patients, treated patients, and healthy controls were analyzed.
- Levels of CH50, C3, C3d, and CICs were quantified.
- Statistical analysis was performed to assess differences and correlations.
Main Results:
- Mean levels of CH50, C3, C3d, and CICs were significantly higher in untreated patients compared to treated patients and controls.
- Higher levels of CH50, C3d, and CICs were observed in untreated patients with far-advanced disease versus moderately advanced disease.
- Significant correlations were found between CICs and C3/C3d in untreated patients, but not in treated patients.
Conclusions:
- Elevated complement activation and CICs in untreated tuberculosis suggest a role in disease pathogenesis.
- The complement system's functional classical pathway and proper activation by CICs may prevent tuberculosis from becoming a typical immune complex disease.
Abstract:
The alterations in serum/plasma levels of total haemolytic complement activity (CH50), complement components C3 and C3d, and circulating immune complexes (CICs) in patients with pulmonary tuberculosis were analysed in relation to the severity of disease and treatment status. The mean levels of CH50, C3, C3d and CICs were significantly higher in untreated than treated patients and in normal controls. In the untreated group, the level of each of these four parameters except C3d was significantly higher in patients with far advanced disease than in those with moderately advanced disease, whereas the difference between treated patients and normal controls was not statistically significant for any of the four parameters tested. There were statistically significant correlations between levels of CICs and both C3 and C3d in the untreated tuberculosis patients. However, the correlations for the same parameters were not significant when treated patients were considered. The CH50 levels in tuberculosis patients suggest a functional classical complement pathway, which is essential for immune complex solubilisation. High C3d level in untreated patients is indicative of increased complement activation, which in turn shows significant correlation with levels of CICs. It appears that the intact and elevated complement proteins and their proper activation by CICs prevents tuberculosis from becoming a typical immune complex disease.