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Combined complete C5 and partial C4 deficiency in humans: clinical consequences and complement-mediated functions in
A Gianella-Borradori1, L Borradori, P M Schneider
1Department of Pediatrics, University Hospital, Lausanne, Switzerland.
Clinical Immunology and Immunopathology
|April 1, 1990
Summary
This study identifies the first human family with combined deficiencies in complement components C5 and C4. These complement deficiencies impair Neisseria infection protection, highlighting the importance of C5 and C4 in immunity.
Area of Science:
- Immunology
- Genetics
- Complement System
Background:
- Recurrent Neisseria meningitidis infections are linked to complement deficiencies, particularly terminal pathway defects.
- Complement component 5 (C5) and complement component 4 (C4) play crucial roles in complement-mediated immunity.
Observation:
- A kindred presented with two siblings experiencing meningococcal meningitis, exhibiting undetectable or severely reduced C5 levels.
- Family members showed heterozygous C5 deficiency, with additional partial deficiencies in C4A and C4B identified in affected individuals.
- This represents the first documented human family with combined C5 and C4 deficiencies.
Findings:
- Repletion with purified C5 restored hemolytic activity in C5-deficient sera.
- Partial C4 deficiency did not impair classical pathway function as assessed by immune precipitation inhibition.
- Alternative pathway function in C5-deficient sera was dependent on the indicator cells and assay conditions, suggesting complex interactions.
Implications:
- Individuals with combined C5 and C4 deficiencies may have insufficient complement activity for protection against Neisserial infections.
- The study underscores the critical role of C5 and C4 in host defense against encapsulated bacteria.
- Understanding these combined deficiencies provides insights into complement system function and its impact on infectious disease susceptibility.