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Introduction to the Complement System definitions

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  • Complement System
    A set of inactive proteins in blood and tissues that initiate immune responses when activated by infection.
  • Innate Immunity
    A non-adaptive immune response that does not change over time and includes the complement system.
  • Adaptive Immunity
    An immune response that adapts over time and is complemented by the classical pathway of the complement system.
  • Alternative Pathway
    One of the three pathways that activate the complement system, independent of antibodies.
  • Lectin Pathway
    A complement system activation pathway that involves lectin binding to pathogen surfaces.
  • Classical Pathway
    A complement system activation pathway that utilizes antibodies and complements adaptive immunity.
  • C3 Convertase
    An enzyme that activates C3 by cleaving it into C3a and C3b, leading to immune responses.
  • C3
    A critical complement protein activated by C3 convertase, leading to opsonization and inflammation.
  • Opsonization
    A process where pathogens are marked for phagocytosis, enhanced by C3b.
  • Inflammation
    An immune response that helps eliminate microbes, triggered by complement activation.
  • Cell Lysis
    The destruction of a cell, often a microbe, as a result of complement system activation.
  • C3a
    An active fragment of C3 that contributes to the inflammatory response.
  • C3b
    An active fragment of C3 that promotes opsonization and cell lysis.
  • Antibodies
    Proteins that the classical pathway uses to complement adaptive immunity.
  • Scanning System
    A function of the complement system to detect signs of microbes in the body.