Complement System Pathways Quiz
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Questions and Answers

What are the three pathways for complement activation?

  • Classical, Lectin, Alternative (correct)
  • Classical, Antibody, Alternative
  • Primary, Secondary, Tertiary
  • Innate, Adaptive, Acquired

In the classical pathway, which molecule is composed of six copies of three different chains?

  • CRP
  • C3 convertase
  • IgG
  • C1 (correct)

What triggers the classical pathway of complement activation?

  • C1q
  • C3 convertase
  • C-reactive Protein
  • Antigen-Antibody Complex (correct)

Which class of antibodies is a more powerful activator of the complement system according to the text?

<p>IgG (D)</p> Signup and view all the answers

What type of protein binds to carbohydrates in the lectin pathway?

<p>Lectin (C)</p> Signup and view all the answers

What binds to C3 convertase (C4b and C2a) in the Classical Pathway to form a C5 convertase?

<p>C3b (B)</p> Signup and view all the answers

Which molecule is recognized by C1q and efficiently activates the classical pathway according to the text?

<p>CRP (D)</p> Signup and view all the answers

Which molecule is recognized by mannose-binding lectin (MBL) in the Lectin Pathway?

<p>Mannose and other repetitive carbohydrate structures (C)</p> Signup and view all the answers

What triggers the Alternative Pathway, making it antigen-antibody complex independent?

<p>C3 (C)</p> Signup and view all the answers

Which of the following is involved in stabilizing the complex of C3b and Factor B in the Alternative Pathway?

<p>Factor P (properdin) (A)</p> Signup and view all the answers

What is formed when C5 is hydrolyzed by C5 convertase in the Classical Pathway?

<p>C5b and C5a (D)</p> Signup and view all the answers

How does Lectin Pathway differ from the Classical Pathway?

<p>Initiation step only (B)</p> Signup and view all the answers

Which step initiates MAC formation in the complement cascade?

<p>Binding of C5b to C6 (A)</p> Signup and view all the answers

How does MAC formation result in cell lysis?

<p>By polymerizing C9 monomers (B)</p> Signup and view all the answers

Which complement receptor is mainly responsible for removing immune complexes from circulation?

<p>CR1 (A)</p> Signup and view all the answers

What is the function of CR1 in the complement cascade?

<p>Binding immune complexes for transport to liver and spleen (A)</p> Signup and view all the answers

Which sequence correctly represents the steps in MAC formation following C5b binding?

<p>C6, C7, C8, addition of C9 monomers (A)</p> Signup and view all the answers

Which complement receptor is specifically present on red blood cells for binding immune complexes?

<p>CR1 (A)</p> Signup and view all the answers

Study Notes

Complement Activation Pathways

  • Three pathways for complement activation: Classical, Lectin, and Alternative

Classical Pathway

  • Composed of six copies of three different chains: C1q molecule
  • Triggered by: Antibody-antigen complexes, specifically IgM or IgG antibodies
  • More powerful activator: IgM antibody

Lectin Pathway

  • Recognition of carbohydrates by: Mannan-binding lectin (MBL) or Ficolins
  • Similar to Classical Pathway, but initiated by binding of MBL to carbohydrates

Alternative Pathway

  • Triggered by: Spontaneous hydrolysis of C3, making it antigen-antibody complex independent
  • Stabilization of C3b and Factor B complex: Properdin

Complement Cascade

  • Formation of C5 convertase: C4b and C2a bind to C3 convertase
  • Hydrolysis of C5 by C5 convertase: Forms C5a and C5b
  • MAC formation initiation: C5b binding
  • MAC formation result: Cell lysis due to formation of a transmembrane channel

Complement Receptors

  • CR1: Mainly responsible for removing immune complexes from circulation
  • Present on red blood cells: CR1, for binding immune complexes
  • Correct sequence for MAC formation: C5b, C6, C7, C8, C9

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Test your knowledge on the Classical and Lectin pathways of the complement system. Learn about the activation, components, and functions of each pathway in the immune response.

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