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Questions and Answers
What are the three pathways for complement activation?
In the classical pathway, which molecule is composed of six copies of three different chains?
What triggers the classical pathway of complement activation?
Which class of antibodies is a more powerful activator of the complement system according to the text?
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What type of protein binds to carbohydrates in the lectin pathway?
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What binds to C3 convertase (C4b and C2a) in the Classical Pathway to form a C5 convertase?
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Which molecule is recognized by C1q and efficiently activates the classical pathway according to the text?
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Which molecule is recognized by mannose-binding lectin (MBL) in the Lectin Pathway?
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What triggers the Alternative Pathway, making it antigen-antibody complex independent?
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Which of the following is involved in stabilizing the complex of C3b and Factor B in the Alternative Pathway?
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What is formed when C5 is hydrolyzed by C5 convertase in the Classical Pathway?
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How does Lectin Pathway differ from the Classical Pathway?
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Which step initiates MAC formation in the complement cascade?
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How does MAC formation result in cell lysis?
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Which complement receptor is mainly responsible for removing immune complexes from circulation?
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What is the function of CR1 in the complement cascade?
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Which sequence correctly represents the steps in MAC formation following C5b binding?
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Which complement receptor is specifically present on red blood cells for binding immune complexes?
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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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Description
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.
