Chapter 07 - Complement System

Question 1

1. The classical complement pathway is activated by
   a. most viruses.
   b. antigen–antibody complexes.
   c. fungal cell walls.
   d. mannose in bacterial cell walls.
2. Which of the following is characteristic of complement
   components?
   a. Normally present in serum
   b. Mainly synthesized by B cells
   c. Present as active enzymes
   d. Heat stable
3. All of the following are true of the recognition unit except
   a. it consists of C1q, C1r, and C1s.
   b. the subunits require calcium for binding together.
   c. binding occurs at the FC region of antibody
   molecules.
   d. C1q becomes an active esterase.
4. Which of the following is referred to as C3 convertase?
   a. C1qrs
   b. C3bD
   c. C3bBb
   d. C4b5a
5. Mannose-binding protein in the lectin pathway is
   most similar to which classical pathway component?
   a. C3
   b. C1rs
   c. C1q
   d. C4
6. Which of the following describes the role of properdin
   in the alternative pathway?
   a. Stabilization of C3/C5 convertase
   b. Conversion of B to Bb
   c. Inhibition of C3 convertase formation
   d. Binding and cleavage of Factor B
7. Which best characterizes the membrane attack
   complex (MAC)?
   a. Each pathway uses different factors to form it.
   b. C5 through C9 are not added in any particular
   order.
   c. One MAC unit is sufficient to lyse any type
   of cell.
   d. C9 polymerizes to form the transmembrane
   channel.
8. All of the following represent functions of the
   complement system except
   a. decreased clearance of antigen–antibody
   complexes.
   b. lysis of foreign cells.
   c. increase in vascular permeability.
   d. migration of neutrophils to the tissues.
9. Which of the following is true of the amplification
   loop in complement activation?
   a. It is only found in the alternative pathway.
   b. The membrane attack unit is amplified.
   c. C3b is the product that is increased.
   d. Increasing amounts of C1qrs are produced.

REVIEW QUESTIONS
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Chapter 7 Complement System 109
10. Factor H acts by competing with which of the
following for the same binding site?
a. Factor B
b. Factor D
c. C3B
d. Factor I
11. A lack of CR1 receptors on RBCs would result in
which of the following?
a. Decreased binding of C3b to RBCs
b. Decreased clearance of immune complexes by the
spleen
c. Decreased breakdown of C1qrs
d. Decreased binding of Factor H
12. Which best describes the role of CR2 on cell
membranes?
a. Binds C1qrs to inactivate it
b. Acts as co-receptor on B cells for antigen
c. Increases clearance of immune complexes
d. Binds particles opsonized with C3b
13. Which of the following best characterizes hemolytic
uremic syndrome?
a. It is a rare cause of renal failure in children.
b. It can be associated with deficiencies in Factor H.
c. The major cause is lack of DAF on RBCs.
d. It is associated with antibody-to-C3 convertase.
14. The CH50 test measures which of the following?
a. Patient serum required to lyse 50% of sensitized
sheep RBCs
b. Functioning of both the classical and alternative
pathways
c. Genetic deficiencies of any of the complement
components
d. Functioning of the lectin pathway only
15. Which of the following would be most effective in
preventing bystander lysis of RBCs?
a. C1-INH
b. Factor B
c. DAF
d. Factor H

16. A decreased CH50 level and a normal AH50 level
    indicate which deficiency?
    a. Decrease in components in the lectin pathway only
    b. Decrease in components in the alternative pathway
    only
    c. Decrease in components of both classical and
    alternative pathways
    d. Decrease in components of the classical pathway
    only
17. Which best describes the role of an anaphylatoxin?
    a. Coats cells to increase phagocytosis
    b. Attracts WBCs to the area of antigen concentration
    c. Increases production of interleukin-1
    d. Increases permeability of blood vessels
18. Which best describes the role of Factor H?
    a. Acts with DAF to break down C3b
    b. Prevents binding of Factor B to C3b
    c. Binds to the C5C6C7 complex
    d. Binds to C1q to shut down the classical pathway
19. A lack of C1-INH might result in which of the
    following conditions?
    a. Paroxysmal nocturnal hemoglobinuria
    b. Hemolytic uremic syndrome
    c. Hereditary angioedema
    d. Increased bacterial infections
20. Which would be most effective in measuring an
    individual complement component?
    a. CH50 assay
    b. Radial immunodiffusion
    c. AH50 assay
    d. Lytic assay with liposome