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Updated: May 12, 2026
08:26
Measuring the 50% Haemolytic Complement (CH50) Activity of Serum
Published on: March 30, 2010
Genetic control of the eighth component of complement.
The Journal of Clinical Investigation
|September 1, 1979
Summary
Extensive structural polymorphism in human complement component 8 (C8) was identified using isoelectric focusing. C8 deficiency is likely a null allele, and heterozygous C8 deficiency cannot be determined by half-normal C8 levels alone.
Area of Science:
- Genetics
- Immunology
- Biochemistry
Background:
- Human complement component 8 (C8) is crucial for the membrane attack complex formation.
- Previous studies have not fully characterized the structural polymorphism of C8.
Purpose of the Study:
- To delineate the structural polymorphism of human C8.
- To investigate the genetic basis of C8 deficiency.
- To determine the inheritance patterns and population frequencies of C8 alleles.
Main Methods:
- Isoelectric focusing in polyacrylamide gel electrophoresis.
- Hemolytic assay for pattern development.
- Population genetics analysis including Hardy-Weinberg equilibrium.
- Family studies including individuals with C8 deficiency.
Main Results:
- Identified extensive structural polymorphism in human C8.
- Delineated gene frequencies for C8 alleles (C8A, C8B, C8A1) across Oriental, Black, and White populations.
- Demonstrated autosomal codominant inheritance for C8.
- Found that C8 deficiency appears to be a null allele at the C8 structural locus.
- Showed that half-normal C8 levels are insufficient to diagnose heterozygous C8 deficiency.
- Confirmed C8 structural locus is not closely linked to human histocompatibility loci.
Conclusions:
- Human C8 exhibits significant structural polymorphism with distinct allele frequencies across different ethnic groups.
- C8 deficiency is genetically linked to a null allele of the C8 structural locus.
- Diagnostic criteria for heterozygous C8 deficiency require further refinement beyond C8 levels.
- The C8 locus is independently inherited from major histocompatibility complex markers.
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