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A case of hereditary combined deficiency of complement components C6 and C7 in man
B P Morgan1, J P Vora, A J Bennett
1Department of Medical Biochemistry, University of Wales College of Medicine, Health Park, Cardiff, UK.
Insights
This study reports a rare combined deficiency of complement components C6 and C7 in a patient with candidiasis and toxoplasmosis. The family analysis revealed heterozygous carriers, highlighting the genetic inheritance of this immune defect.
Area of Science:
- Immunology
- Genetics
- Complement System
Background:
- The complement system is crucial for innate and adaptive immunity.
- Deficiencies in complement components can lead to increased susceptibility to infections.
- Complement C6 and C7 are essential for the formation of the membrane attack complex.
Observation:
- A patient presented with recurrent candidiasis and toxoplasmosis.
- Immunological investigation identified a total deficiency of complement C6.
- Low levels of apparently normal complement C7 were also detected in the patient's serum.
Findings:
- This case represents a combined homozygous deficiency of complement C6 and C7.
- Family studies confirmed heterozygous carriers for this combined deficiency.
- This is the second reported instance of combined C6 and C7 deficiency and the third kindred identified.
Implications:
- Combined C6 and C7 deficiency predisposes individuals to infections, particularly Neisseria species.
- Understanding these deficiencies aids in diagnosing and managing recurrent infections.
- This finding contributes to the knowledge of complement system genetics and function.
Abstract:
Immunological investigation of a patient presenting with candidiasis and toxoplasmosis revealed a combined deficiency of C6 and C7. Deficiency of C6 was total, but small amounts (less than 1 microgram/ml) of apparently normal C7 were present in the serum. All family members (three sibs and both parents) were heterozygous for the combined deficiency. This is only the second reported case of combined homozygous deficiency of the closely linked and immunochemically similar proteins C6 and C7, and only the third kindred in which this defect has been demonstrated.