Questions and Answers
The classical complement pathway is activated by which of the following?
Which of the following is characteristic of complement components?
All of the following are true of the recognition unit except:
Which of the following is referred to as C3 convertase?
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Mannose-binding protein in the lectin pathway is most similar to which classical pathway component?
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Which of the following describes the role of properdin in the alternative pathway?
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Which best characterizes the membrane attack complex (MAC)?
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All of the following represent functions of the complement system except:
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Which of the following is true of the amplification loop in complement activation?
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Factor H acts by competing with which of the following for the same binding site?
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A lack of CR1 receptors on RBCs would result in which of the following?
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Which best describes the role of CR2 on cell membranes?
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Which of the following best characterizes hemolytic uremic syndrome?
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The CH50 test measures which of the following?
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Which of the following would be most effective in preventing bystander lysis of RBCs?
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A decreased CH50 level and a normal AH50 level indicate which deficiency?
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Which best describes the role of Factor H?
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Study Notes
Classical Complement Pathway
- Activated by antigen-antibody complexes.
- Key in immune response against pathogens.
Complement Components
- Present in serum, serve critical functions in immune processes.
- Not actively synthesized by B cells; primarily produced by liver.
Recognition Unit of Complement
- Composed of C1q, C1r, and C1s.
- Requires calcium for subunit binding.
- C1q does not become an active esterase.
C3 Convertase
- Identified as C3bBb, crucial for the complement activation cascade.
Mannose-binding Protein
- Functions similarly to C1q in the lectin pathway, aiding in pathogen recognition.
Role of Properdin
- Stabilizes C3/C5 convertase in the alternative pathway, enhancing complement activation.
Membrane Attack Complex (MAC)
- Formed by C5 through C9 components.
- C9 polymerizes to create transmembrane channels that lysate cells.
Functions of the Complement System
- Promotes lysis of foreign cells, increases vascular permeability, and facilitates neutrophil migration.
- Does not decrease clearance of antigen-antibody complexes; this would be detrimental.
Amplification Loop
- Key feature in complement activation, primarily in the alternative pathway.
- C3b is significantly increased during this process.
Factor H
- Competes with Factor B for binding sites, regulating complement activation.
CR1 Receptors on RBCs
- Their absence leads to decreased clearance of immune complexes by the spleen.
Role of CR2
- Acts as a co-receptor for antigen on B cells, enhancing immune responses.
Hemolytic Uremic Syndrome
- Potential association with deficiencies in Factor H, impacting renal function.
CH50 Test
- Measures serum's ability to lyse 50% of sensitized sheep RBCs, assessing complement pathway functioning.
Prevention of Bystander Lysis
- DAF (Decay Accelerating Factor) is effective in preventing unintended RBC lysis.
Complement Deficiencies Indication
- Decreased CH50 indicates deficits in classical pathway components.
- Normal AH50 suggests alternative pathway components are intact.
Role of Factor H
- Inhibits Factor B binding to C3b, crucial for regulating the alternative pathway.
Anaphylatoxins
- Important mediators that enhance inflammation and recruit immune cells during complement activation.
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Description
Explore the classical complement pathway and its components in this quiz. Test your knowledge on the roles of various proteins in immune responses and how they interact in the complement activation cascade. Understand the critical functions of the complement system in defending against pathogens.
