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Related Concept Videos

Complement System01:27

Complement System

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The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a...
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A complementation test is a simple cross to identify whether the two mutations are located on the same gene or different genes. It was first performed by Edward Lewis in the 1940s while working on fruit flies. He developed the test to identify the location and arrangement of different mutations on chromosomes.
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Tissue-specific transcription factors contribute to diverse cellular functions in mammals. For example, the gene for beta globin, a major component of hemoglobin, is present in all cells of the body. However, it is only expressed in red blood cells because the transcription factors that can bind to the promoter sequences of the beta globin gene are only expressed in these cells. Tissue-specific transcription factors also ensure that mutations in these factors may impair only the function of...
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Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
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Transcription elongation is a dynamic process that alters depending upon the sequence heterogeneity of the DNA being transcribed. Hence, it is not surprising that the elongation complex's composition also varies along the way while transcribing a gene.
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Drug distribution in the human body is a complex process influenced by various individual factors, including age, pregnancy, obesity, diet, body water composition, pH levels, and specific disease conditions.
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Updated: Jan 24, 2026

Depletion of Specific Cell Populations by Complement Depletion
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The story of complement factor I.

Peter J Lachmann1

  • 1Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 0ES, United Kingdom.

Immunobiology
|May 22, 2019
PubMed
Summary
This summary is machine-generated.

Complement Factor I, discovered in 1966, regulates the alternative complement pathway. Gene therapy using Factor I for age-related macular degeneration reached clinical use in 2019, overcoming decades of research challenges.

Keywords:
Age related degenerationC3b breakdown cycleC3b feedback cycleComplementConglutininFactor I

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Area of Science:

  • Immunology
  • Complement System Biology
  • Gene Therapy

Background:

  • Complement Factor I (CFI) was discovered in 1966.
  • A patient with CFI deficiency presented with a hyperactive alternative complement pathway, leading to complement consumption and secondary deficiency.
  • This case elucidated the mechanism of the alternative pathway.

Purpose of the Study:

  • To review the historical progression of complement Factor I research.
  • To trace the journey from initial observations of CFI's role in complement regulation to its clinical application.
  • To highlight the development of gene therapy for age-related macular degeneration utilizing CFI.

Main Methods:

  • Historical literature review of complement Factor I research.
  • Analysis of key discoveries and clinical milestones.
  • Examination of the development of gene therapy vectors for CFI delivery.

Main Results:

  • Factor I deficiency leads to alternative pathway hyperactivity and complement consumption.
  • Elevating Factor I levels can down-regulate the alternative pathway.
  • The first clinical application of CFI gene therapy for age-related macular degeneration occurred in 2019.

Conclusions:

  • Complement Factor I plays a critical role in regulating the complement system.
  • Decades of research were required to translate the understanding of Factor I into clinical therapies.
  • Gene therapy represents a significant advancement in treating complement-mediated diseases like age-related macular degeneration.