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Review of the Complement System quiz

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  • What are the three pathways that activate the complement system?
    The three pathways are the alternative pathway, lectin pathway, and classical pathway.
  • What triggers the alternative pathway of complement activation?
    The alternative pathway is triggered by C3b binding to the surface of invading microbes.
  • How does the lectin pathway activate the complement system?
    The lectin pathway is activated when mannose-binding lectin (MBL) binds to mannose on the surface of microbes.
  • What initiates the classical pathway of complement activation?
    The classical pathway is initiated when antibodies from the adaptive immune system bind to antigens on microbes.
  • What is the common enzyme produced by all three complement activation pathways?
    All three pathways produce 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 are the two fragments produced when C3 is cleaved?
    C3 is cleaved into C3a and C3b.
  • What role do C3a and C5a play after complement activation?
    C3a and C5a trigger inflammatory responses to help eliminate microbes.
  • How does C3b enhance phagocytosis?
    C3b acts as an opsonin, improving the effectiveness of phagocytosis by phagocytes.
  • What is opsonization in the context of the complement system?
    Opsonization is the process where C3b coats microbes, making them easier for phagocytes to engulf.
  • How can C3b lead to microbe cell lysis?
    C3b interacts with other complement proteins to form membrane attack complexes that create pores in microbe membranes.
  • What type of bacteria are especially targeted by membrane attack complexes?
    Gram-negative bacteria are especially targeted by membrane attack complexes.
  • Why is the classical pathway important for the complement system's name?
    The classical pathway allows the complement system to complement adaptive immunity, hence its name.
  • What is the relationship between innate and adaptive immunity in the classical pathway?
    The classical pathway shows crosstalk, as antibodies from adaptive immunity trigger the complement system, which is part of innate immunity.
  • Where are inactive complement proteins found before activation?
    Inactive complement proteins circulate in the blood and tissues.