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Activation Pathways of the Complement System quiz

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  • What are the three activation pathways of the complement system?
    The three pathways are the alternative, lectin, and classical pathways.
  • What is the common enzyme formed by all three complement activation pathways?
    All three pathways converge at the formation of the enzyme C3 convertase.
  • What triggers the alternative pathway of complement activation?
    The alternative pathway is triggered by the binding of complement protein C3b to surface molecules of invading microbes.
  • What immune responses are generated after C3 convertase formation?
    C3 convertase formation leads to opsonization, cell lysis, and inflammation.
  • How does the lectin pathway activate the complement system?
    The lectin pathway uses mannose-binding lectins (MBLs) that bind to mannose on microbial surfaces to activate the complement system.
  • What type of molecule is mannose-binding lectin (MBL)?
    MBL is a lectin, which is a protein that binds carbohydrates.
  • Where is mannose commonly found in the context of the lectin pathway?
    Mannose is commonly found on the cell surfaces of bacteria and fungi.
  • What is the role of antibodies in the classical pathway?
    Antibodies produced by adaptive immunity bind to antigens on microbes, triggering the classical pathway.
  • What is an antigen in the context of the complement system?
    An antigen is any toxin or foreign substance that induces an antibody immune response.
  • What happens when antibodies bind to antigens on microbial surfaces in the classical pathway?
    Bound antibodies interact with complement proteins, leading to the formation of C3 convertase.
  • What does C3 convertase do in the complement system?
    C3 convertase cleaves the complement protein C3 into C3a and C3b.
  • What is the function of C3a in the complement system?
    C3a promotes inflammation as part of the immune response.
  • What is the function of C3b in the complement system?
    C3b leads to opsonization and cell lysis of microbes.
  • How does the alternative pathway amplify the immune response?
    The pathway is amplified by cleaving more C3 to produce more C3b, which binds to microbes and triggers further immune responses.
  • Why is the complement system considered to complement adaptive immunity?
    The classical pathway uses antibodies from adaptive immunity to activate the complement system, thus complementing adaptive immune responses.