Deck 5: The Complement System

Question 1

Which of the following complement fixation pathways can be initiated by a soluble C3 convertase?

A)Alternative
B)Classical
C)Lectin
D)All of the answers are correct.
E)None of the answers are correct.

Answer 1

A

Question 2

On a holistic scale, the complement system plays a role in

A)specific pathogen defenses.
B)nonspecific pathogen defenses.
C)both specific and nonspecific pathogen defenses.
D)All of the answers are correct.
E)None of the answers are correct.

Answer 2

C

Question 3

Complement components can be classified into seven functional categories, including

A)Enzymatic mediators.
B)Inflammatory mediators.
C)Membrane attack proteins.
D)Regulatory complement components.
E)All the answers are correct.

Answer 3

E

Question 4

Of the molecules listed, which can be considered the key molecule in complement pathways?

A)C1
B)IgM
C)MBL
D)C5 convertase
E)None of the answers are correct.

Question 5

In considering the following list of molecules, which can act as a bridge to connect complement labeled pathogens to effector immune cells?

A)IgM
B)C1
C)C1R
D)C3aR
E)Both C1R and C3aR are correct.

Question 6

Which of the following provides serine protease activity in the classical complement activation pathway?

A)MASP-2
B)C1r
C)C1s
D)Both C1r and C1s act in the classical pathway.
E)None of the answers acts in the classical pathway.

Question 7

Which of the following is the MOST potent anaphylatoxin produced during the complement cascade?

A)C3a
B)C3b
C)C5a
D)C5b
E)Ba

Question 8

To which of the following is MBL MOST structurally similar?

A)C3b
B)C1q
C)Bb
D)C5b
E)None of the answers are correct.

Question 9

Which of the following is TRUE about the C5 convertase?

A)C5 convertase can consist of the membrane-bound components C3b₂Bb.
B)C5 convertase cleaves C5 into C5a and C5b, with the b chain attached to the pathogen surface and the ? chain dissociating away to serve as a potent proinflammatory chemotactic factor
C)C5 convertase is an important player in the production of the MAC.
D)All of the answers are true.
E)None of the answers are true.

Question 10

Which of the following BEST explains the timing of the classical pathway of complement fixation, relative to the other pathways of complement fixation, against a pathogen in an individual who has never been exposed to said pathogen?

A)No target for C1qrs exists on the surface of the pathogen in the earliest stages of the response to it.
B)The chemical environment of the pathogen's surface favors the spontaneous activation of soluble C3 immediately upon exposure to the pathogen.
C)C1qrs immediately recognizes carbohydrate antigens on the surface of the pathogen, allowing for rapid formation of the C4b2a C3 convertase.
D)The pathogen expresses one or more factors on its surface that act as negative regulators of C3 convertase formation.
E)None of the answers are correct.

Question 11

Which of the following binds to surface-bound C3b during formation of the alternative C3 convertase?

A)Factor Bb
B)Factor B
C)C2a
D)C4b
E)Factor D

Question 12

Which of the following can be directly activated as a soluble protein in the microenvironment surrounding a pathogenic cell?

A)C2
B)C3
C)Factor B
D)Factor D
E)C4

Question 13

Which of the following acts as a protease that is required to generate the alternative pathway C3 convertase?

A)C2
B)C3
C)Factor B
D)Factor D
E)C4

Question 14

Which of the following is the first complement factor to be activated, resulting in insertion of one of its subunits into the pathogen surface in two of the three complement fixation pathways?

A)C2
B)C3
C)Factor B
D)Factor D
E)C4

Question 15

Which of the following, when activated itself, acts as a protease that converts soluble C3 into C3a and C3b in the alternative pathway?

A)C2
B)C3
C)Factor B
D)Factor D
E)C4

Question 16

Which of the following, when activated, utilizes its "a" component instead of the "b" component in the formation of the C3 convertase?

A)C2
B)C3
C)Factor B
D)Factor D
E)C4

Question 17

Which of the following immunoglobulin isotypes is the MOST efficient at initiating a complement fixation cascade?

A)IgG
B)IgE
C)IgM
D)IgD
E)None of the answers are correct.

Question 18

Addition of which of the following components to any C3 convertase leads to the formation of the C5 convertase?

A)C3b
B)C2a
C)C4b
D)C5b
E)C3a

Question 19

Which form of IgM is MOST readily recognized by C1q?

A)Monomeric IgM
B)Planar pentameric IgM
C)"Staple-form" pentameric IgM
D)All of the answers are recognized equally by C1q.
E)None of the answers are recognized by C1q.

Question 20

Which of the following acts as a positive regulator of complement fixation via stabilization of C3bBb?

A)DAF (CD55)
B)Properdin
C)Factor H
D)Factor I
E)MCP (CD46)

Question 21

Which of the following acts as a serine protease that, with cofactors, cleaves C3b and C4b?

A)DAF (CD55)
B)Properdin
C)Factor H
D)Factor I
E)MCP (CD46)

Question 22

Which of the following facilitates dissociation of both the C4b2a and C3bBb C3 convertases?

A)DAF (CD55)
B)Properdin
C)Factor H
D)Factor I
E)MCP (CD46)

Question 23

Which of the following is capable of initiating the alternative pathway of complement fixation by directly binding to the surfaces of certain cell types?

A)DAF (CD55)
B)Properdin
C)Factor H
D)Factor I
E)MCP (CD46)

Question 24

The MAC consists of a multimeric complex of which of the following proteins that, by their association, forms a pore in the surface of the attacked cell?

A)C3b
B)C5b
C)C6
D)C9
E)C4b

Question 25

How does binding of complement-opsonized microbes to CR1 facilitate clearing of the microbe from the host?

A)Promotion of phagocytosis of opsonized microbes by leukocytes
B)Secretion of proinflammatory cytokines
C)Mediating phagocytosis of C3b-opsonized pathogen by B cells
D)All of the answers occur as a result of CR1 binding of complement-opsonized microbes.
E)None of the answers occur.

Question 26

Which of the following is TRUE about the binding of C5b to the pathogen surface?

A)C5b binds to the pathogen surface the same way C4b and C3b do.
B)C5b requires C6 binding to stabilize it before it dissociates away.
C)C5b, when complexed to C6 and C7, is capable of forming the MAC on any cell membrane, pathogen, or host.
D)C5b both requires C6 binding to stabilize it before it dissociates away and, when complexed to C6 and C7, is capable of forming the MAC on any cell membrane, pathogen, or host.
E)All of the answers are true.

Question 27

Which of the following is NOT an effect of C3a and C5a binding their receptors on leukocytes?

A)Increased vascular permeability via induction of TNF- ? and IL-6 secretion
B)Induction of degranulation by granulocytes
C)Increased smooth muscle contraction to aid in delivering immune cells and molecules to the site of infection
D)All of the answers are effects of C3a and C5a binding their receptors.
E)None of the answers are effects of C3a and C5a binding their receptors.

Question 28

Which of the following regulates complement function by directly inhibiting formation of the MAC?

A)Protectin (CD59)
B)Factor I
C)DAF (CD55)
D)C1INH
E)Factor H

Question 29

Based on your knowledge of complement activation pathways, predict which group of pathogens would be MOST susceptible to lysis by MACs.

A)Gram-negative pathogens
B)Eukaryotic pathogens
C)Enveloped viruses
D)Gram-positive pathogens
E)Gram-negative pathogens and enveloped viruses are equally susceptible.

Question 30

A common denominator among the three complement pathways is antigen recognition.Can you name three molecules that act as antigen recognition molecules for the classical, lectin, and alternative pathways?

Question 31

You suspect that you have identified a mouse line that lacks a functional complement system.A friend suggests collecting serum and looking for hemolytic activity as a first screen in determining complement activity in the line.Do you agree or disagree with your friend, and why?

Question 32

In your own words, and using no more than two sentences, explain how DAF regulates complement to inhibit MAC-mediated lysis.

Question 33

Name two complement proteins whose primary functions are promoting anaphylatoxin activity.What common structural feature of the two named proteins allows for their inactivation by way of serum carboxypeptidases?

Question 34

Can you imagine how a blood-borne bacterial pathogen might activate all three arms of the complement system? How can this occur?

Question 35

Complement activation is implicated in the pathogenesis of SLE.However, the incidence of SLE is highly correlated to C4 deficiency.Can you explain this paradox?

Question 36

Some strains of staphylococcal bacteria express staphylokinase.Staphylokinase can degrade IgG.Based on this information, how will staphylokinase disrupt complement? Which pathway is most impacted?

Question 37

During an immune response, host damage from complement is generally limited to the area in which complement is activated.Explain one property of complement proteins that contribute to this observation.

Question 38

Complement is subject to rigorous regulatory mechanisms.C1INH can inhibit both the classical and lectin pathways.What function feature of C1INH allows for inhibition of both pathways?

Question 39

Initially the complement system was characterized by its capacity to covert antibody binding into pathogen lysis.Does the discovery of MAC-mediated lysis align with the evolutionary history of the complement system?