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Review of the Complement System quiz

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  • What are the three pathways that can activate the complement system?
    The three pathways are the alternative pathway, lectin pathway, and classical pathway.
  • What triggers the alternative pathway of the complement system?
    The alternative pathway is triggered by C3b binding to the surface of invading microbes.
  • How is the lectin pathway activated in the complement system?
    The lectin pathway is activated when mannose binding lectin (MBL) binds to mannose on microbial surfaces.
  • What initiates the classical pathway of the complement system?
    The classical pathway is initiated when antibodies from the adaptive immune system bind to antigens on microbes.
  • What is the common enzyme formed by all three complement activation pathways?
    All three pathways lead to the formation of the enzyme C3 convertase.
  • What does C3 convertase do in the complement system?
    C3 convertase cleaves the inactive protein C3 into C3a and C3b.
  • What is the role of C3a in the immune response?
    C3a triggers inflammation to help eliminate microbes.
  • How does C3b enhance phagocytosis?
    C3b acts as an opsonin, allowing phagocytes to more effectively phagocytose microbes.
  • What is opsonization?
    Opsonization is the process by which opsonins like C3b coat microbes to enhance their uptake by phagocytes.
  • How can C3b lead to microbial cell lysis?
    C3b interacts with other complement proteins to form membrane attack complexes that create pores in microbial membranes.
  • What type of bacteria are especially targeted by membrane attack complexes?
    Gram-negative bacteria are especially targeted by membrane attack complexes.
  • What is the significance of the classical pathway in immunity?
    The classical pathway links innate immunity (complement system) with adaptive immunity (antibodies).
  • What is the function of mannose binding lectin (MBL) in the complement system?
    MBL binds to mannose on microbial surfaces, triggering the lectin pathway and complement activation.
  • Which complement proteins, besides C3a, can trigger inflammation?
    C5a, along with C3a, can trigger the inflammatory response.
  • Where are inactive complement proteins found before activation?
    Inactive complement proteins circulate in the blood and tissues.