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Hereditary human complement C3 deficiency owing to reduced levels of C3 mRNA

A G Ulbrich1, M P Florido, V Nudelman

  • 1Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brasil.

Scandinavian Journal of Immunology
|June 26, 2001
PubMed

Insights

A child with recurrent infections had severely low complement component 3 (C3) levels, indicating a critical role for C3 in immune defense. Genetic analysis revealed significantly reduced C3 messenger RNA (mRNA) in his cells.

Area of Science:

  • Immunology
  • Genetics
  • Molecular Biology

Background:

  • Recurrent bacterial infections and vasculitis can indicate underlying primary immunodeficiencies.
  • The complement system, particularly complement component 3 (C3), is crucial for innate and adaptive immunity.

Observation:

  • An 8-year-old presented with recurrent infections and vasculitis, exhibiting extremely low serum C3 levels.
  • The patient's serum showed impaired classical and alternative complement pathway hemolytic activities.

Findings:

  • In vitro addition of purified C3 restored the classical pathway hemolytic activity, suggesting C3 deficiency.
  • Analysis of fibroblast supernatants revealed an absence of C3 alpha and beta chains.
  • Reverse transcription-polymerase chain reaction (RT-PCR) assays demonstrated significantly reduced C3 mRNA synthesis in the patient's fibroblasts.

Implications:

  • This case highlights a severe genetic defect in C3 production, leading to immunodeficiency.
  • Understanding C3 deficiency is vital for diagnosing and managing patients with recurrent infections and complement abnormalities.
  • Further research into complement component deficiencies can elucidate their role in various autoimmune and infectious diseases.

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