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Alpha 1-antitrypsin deficiency, complement activation, and chronic liver disease
E T Littleton1, L Bevis, L J Hansen
1Department of Immunology, King's College School of Medicine and Dentistry, London.
Insights
Children with alpha 1-antitrypsin (AT) deficiency show increased complement system activation, particularly in severe liver disease. This suggests the complement system plays a role in the liver damage associated with alpha 1-AT deficiency.
Area of Science:
- Immunology
- Hepatology
- Genetics
Background:
- The complement system is a key mediator of inflammation, regulated by inhibitors like alpha 1-antitrypsin (AT).
- Alpha 1-AT deficiency is a genetic disorder linked to chronic liver disease in children.
- Understanding complement system's role in alpha 1-AT deficiency-related liver disease is crucial.
Purpose of the Study:
- To investigate complement system activation in children with alpha 1-AT deficiency and varying degrees of liver disease.
- To determine if complement activation correlates with the severity of liver disease in alpha 1-AT deficiency.
Main Methods:
- Studied 34 children with alpha 1-AT deficiency (minimal, moderate, severe liver disease) and 38 healthy controls.
- Measured complement components C3, C4, and the C3d fragment.
- Calculated the C3d:C3 ratio as a marker of complement activation.
Main Results:
- Children with severe liver disease had lower C3 and C4 levels, suggesting impaired protein synthesis or complement consumption.
- The C3d fragment was elevated in all alpha 1-AT deficiency patient groups compared to controls.
- The C3d:C3 ratio increased with disease severity, indicating heightened complement activation.
Conclusions:
- Complement activation is elevated in children with alpha 1-AT deficiency.
- The degree of complement activation correlates with the severity of liver disease.
- The complement system may contribute to the pathogenesis of chronic liver disease in alpha 1-AT deficiency.
Abstract:
Activation of the complement system, the main humoral mediator of inflammation, is restrained by the action of enzyme inhibitors including alpha 1-antitrypsin. Deficiency leads to chronic liver disease in about one in five children with this genetic defect. Complement activation was investigated in 34 children with alpha 1 AT deficiency (12 with minimal, 10 with moderate, and 12 with severe liver disease) and in 38 sex and age matched normal children by measuring the complement parent molecules C3, C4, the C3d fragment and by calculating the C3d:C3 ratio. C3 and C4 were lower in children with severe liver disease compared with controls, indicating impairment of hepatic protein synthesis or complement consumption. The C3d activation fragment was higher in all the patient groups when compared with controls while the C3d:C3 ratio, a measure of activation independent of the concentrations of the parent molecule, was higher in patients than in controls and increased with the degree of disease severity. These results suggest that complement may have a role in the pathogenesis of the chronic liver disease associated with alpha 1AT deficiency.