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Introduction to the Complement System definitions

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  • Complement System
    A network of inactive blood and tissue proteins that, upon activation, triggers immune responses like microbe removal and inflammation.
  • Innate Immunity
    A non-adaptable defense mechanism present from birth, providing immediate response to infections without prior exposure.
  • Adaptive Immunity
    A specific immune defense that utilizes antibodies and improves with repeated exposure to pathogens.
  • Antibody
    A protein produced by adaptive immunity that binds to specific antigens, aiding in pathogen detection and elimination.
  • Alternative Pathway
    A complement activation route that does not require antibodies and is triggered directly by microbial surfaces.
  • Lectin Pathway
    A complement activation route initiated by binding of lectin proteins to microbial carbohydrates.
  • Classical Pathway
    A complement activation route that relies on antibodies to recognize and bind to pathogens.
  • C3 Convertase
    An enzyme complex formed during complement activation that cleaves C3 into its active fragments.
  • C3
    A central complement protein that, when cleaved, generates fragments essential for immune responses.
  • C3a
    An active fragment produced from C3 cleavage that promotes inflammation during immune responses.
  • C3b
    An active fragment from C3 cleavage that enhances phagocytosis and can lead to cell lysis.
  • Opsonization
    A process where pathogens are marked for enhanced phagocytosis by immune cells.
  • Cell Lysis
    The destruction of a cell's membrane, resulting in the breakdown and death of the cell.
  • Inflammation
    A localized immune response characterized by redness, heat, and swelling, aiding in microbe elimination.
  • Phagocytosis
    The engulfment and digestion of microbes or particles by immune cells, often enhanced by complement activation.