Lecture 5 - Complement
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Questions and Answers

What role do C3a and C5a play in inflammation?

  • Suppress the opsonization of pathogens
  • Inhibit the release of proinflammatory cytokines
  • Recruit phagocytes and promote inflammation (correct)
  • Prevent anaphylactic shock

    • How do complement receptors connect complement-tagged pathogens to effector cells?

  • Through inhibition of proinflammatory cytokine release
  • By stimulating the release of granule components from phagocytes
  • By facilitating the binding of complement-tagged pathogens to effector cells (correct)
  • By promoting pathogen lysis

    • How does opsonization enhance phagocytosis?

  • Prevents pathogen lysis
  • Makes pathogens more readily taken up by phagocytosis (correct)
  • Reduces the uptake of pathogens by phagocytes
  • Promotes inflammation

    • What is the function of properdin (factor P) in the alternative pathway of complement activation?

    <p>Stabilizes C3 convertase (C3bBb)</p> Signup and view all the answers

    Which complement factor creates the membrane-attack complex (MAC) that leads to pathogen lysis?

    <p>Multiple complement factors</p> Signup and view all the answers

    What is the main downstream effect of large amounts of C3a and C5a?

    <p>Anaphylactic shock</p> Signup and view all the answers

    What is the key mechanism of action of the complement system related to inflammation?

    <p>Increasing vascular permeability and chemotaxis</p> Signup and view all the answers

    Which process involves the coating of a pathogen's surface to make it more easily ingested by phagocytes?

    <p>Opsonization</p> Signup and view all the answers

    What is the main function of phagocytosis in cellular processes?

    <p>Facilitating engulfment of pathogens</p> Signup and view all the answers

    How is the complement system initially activated?

    <p>Via three pathways: Classical, Alternative, Lectin</p> Signup and view all the answers

    Which proteins circulate in the blood until activated and initiate their respective complement reactions?

    <p>Pro-proteases</p> Signup and view all the answers

    Which fragment of the complement system identified by 'a' after its name has a specific function?

    <p>'a' fragment</p> Signup and view all the answers

    What is the main function of C3 convertase in the complement system?

    <p>Cleave C3 into C3a and C3b</p> Signup and view all the answers

    What is the role of negative regulation in complement activation?

    <p>Preventing excessive activation and damage to host tissues</p> Signup and view all the answers

    Which pathway is triggered by soluble proteins known as lectins?

    <p>Lectin pathway itself</p> Signup and view all the answers

    What is the role of pro-proteases in the complement system?

    <p>Initiate complement reactions by cleaving and activating the next protein in the sequence</p> Signup and view all the answers

    What is one of the main outcomes of inhibiting the formation of MAC on host cells?

    <p>Protection of host cells from damage</p> Signup and view all the answers

    Which protein prevents the appearance of C3 convertase under normal/basal conditions?

    <p>CD59 (Protectin)</p> Signup and view all the answers

    Which molecule is involved in enhancing inflammation according to the text?

    <p>C3a</p> Signup and view all the answers

    What is the main function of C3b as discussed in the text?

    <p>Opsonization</p> Signup and view all the answers

    Which protein is involved in the negative regulation of MAC formation by inhibiting the assembly of the Membrane Attack Complex?

    <p>CD59 (Protectin)</p> Signup and view all the answers

    Which pathway results in the generation of C3 convertase (C4b2a) according to the text?

    <p>Classical pathway</p> Signup and view all the answers

    What is the function of C3b in the complement system?

    <p>Pathogen lysis</p> Signup and view all the answers

    What initiates an amplification loop for C3b formation in the alternative pathway?

    <p>Factor B and protease factor D</p> Signup and view all the answers

    Which outcome is NOT associated with complement activation?

    <p>Pathogen growth promotion</p> Signup and view all the answers

    Which molecule is involved in phagocytosis enhancement in the complement system?

    <p>C3b</p> Signup and view all the answers

    What happens under normal/basal conditions due to the presence of complement-regulatory proteins?

    <p>Prevention of complement activation progression</p> Signup and view all the answers

    What is the role of C1q in the complement system based on the text?

    <p>Directly binding pathogens</p> Signup and view all the answers

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