The Complement System

Question 1

What type of proteins make up the complement system?

A) Heat-stable proteins
B) Heat-labile proteins
C) Structural proteins
D) Lipid-based proteins

Answer 1

Answer: B

Question 2

Who first described and coined the term “complement”?

A) Jules Bordet
B) Paul Ehrlich
C) Louis Pasteur
D) Robert Koch

Answer 2

Answer: B

Question 3

What is the major function of the complement system?

A) Oxygen transport
B) Cell lysis and opsonization
C) Blood clotting
D) Hormone regulation

Answer 3

Answer:B

Question 4

Which organ produces most complement proteins?

A) Kidney
B) Liver
C) Spleen
D) Pancreas

Answer 4

B

Question 5

Which complement component is involved in opsonization?

A) C3b
B) C5a
C) C6
D) C9

Answer 5

A

Question 6

How many major pathways are involved in complement activation?

A) One
B) Two
C) Three
D) Four

Answer 6

C

Question 7

Which complement activation pathway is considered the most ancient?

A) Classical pathway
B) Alternative pathway
C) Lectin pathway
D) None of the above

Answer 7

Answer: C

Question 8

What is the main molecule required to activate the classical pathway?

A) Antigen
B) Antibody
C) C3
D) IgG or IgM

Answer 8

D

Question 9

What is unique about the alternative pathway?

A) It bypasses C1, C4, and C2
B) It requires antibodies
C) It is not part of the innate immune system
D) It is found only in bacteria

Answer 9

Answer: A

Question 10

Which component is the pivotal molecule in complement activation?

A) C1
B) C2
C) C3
D) C5

Answer 10

C

Question 11

Which of the following is an anaphylatoxin?

A) C3b
B) C5a
C) C9
D) Factor B

Answer 11

B

Question 12

The membrane attack complex (MAC) is composed of which proteins?

A) C1, C2, C3
B) C3b, C4a, C5a
C) C5b, C6, C7, C8, C9
D) Factor B, Factor D, Properdin

Answer 12

Answer: C

Question 13

Which component is the most potent opsonin?

A) C3a
B) C3b
C) C5a
D) C6

Answer 13

B

Question 14

What is the function of complement receptors?

A) Binding complement proteins to signal cellular functions
B) Activating antibodies
C) Destroying red blood cells
D) None of the above

Answer 14

Answer: A

Question 15

What is the function of anaphylatoxins?

A) Induce inflammation
B) Promote blood clotting
C) Increase antibody production
D) Directly kill bacteria

Answer 15

Answer: A

Question 16

Why is complement regulation important?

A) To prevent excessive inflammation and tissue damage
B) To increase bacterial resistance
C) To enhance blood clotting
D) To decrease immune response

Answer 16

Answer: A

Question 17

What does C1 inhibitor (C1INH) do?

A) Blocks C3 cleavage
B) Prevents formation of MAC
C) Detaches C1r and C1s from C1q
D) Inactivates Factor B

Answer 17

C

Question 18

Which regulatory protein prevents insertion of C9 into the membrane?

A) Factor H
B) Decay-accelerating factor (DAF)
C) CD59 (MIRL)
D) C1INH

Answer 18

C

Question 19

Which factor inactivates C3b?

A) Factor H
B) Factor I
C) Factor B
D) Properdin

Answer 19

Answer: B

Question 20

Which complement regulator prevents bystander effect?

A) Factor H
B) Decay-accelerating factor (DAF)
C) Factor B
D) C5a

Answer 20

B

Question 21

Which deficiency is the most common complement deficiency?

A) C3
B) C4
C) C2
D) C5

Answer 21

C

Question 22

Which deficiency leads to severe recurrent infections?

A) C2
B) C3
C) C5
D) C9

Answer 22

B

Question 23

A deficiency in which protein leads to hereditary angioedema?

A) C1INH
B) C2
C) C5
D) Factor H

Answer 23

A

Question 24

Which disease is associated with DAF (CD55) deficiency?

A) Systemic lupus erythematosus (SLE)
B) Paroxysmal nocturnal hemoglobinuria (PNH)
C) Atherosclerosis
D) Neisseria infections

Answer 24

Answer: B

Question 25

What condition is associated with properdin deficiency? A) Neisseria infections B) Pneumonia C) Tuberculosis D) Asthma

Answer 25

A

Question 26

What is the traditional method for measuring C3 and C4 levels? A) ELISA B) Radial immunodiffusion C) Western blot D) Flow cytometry

Answer 26

B

Question 27

Which method is used in the CH50 assay? A) Hemolysis of antibody-sensitized sheep RBCs B) Western blot C) PCR D) Electron microscopy

Answer 27

Answer: A

Question 28

What does ELISA detect in complement assays? A) C3 concentration B) Neo-epitopes on C9 C) Factor B D) Hemolysis rate

Answer 28

B

Question 29

Which anticoagulant is used to preserve complement proteins? A) Heparin B) EDTA C) Citrate D) Warfarin

Answer 29

B

Question 30

What temperature is used to inactivate complement in vitro? A) 37°C B) 56°C C) 100°C D) 4°C

Answer 30

B

Question 31

What stabilizes the C1 complex in the classical pathway? A) Magnesium ions B) Calcium ions C) Sodium ions D) Potassium ions

Answer 31

Answer: B

Question 33

Which immunoglobulin is the most efficient at fixing complement? A) IgA B) IgG C) IgE D) IgM

Answer 33

D

Question 34

What complement component is the first to be cleaved in all pathways? A) C1 B) C2 C) C3 D) C5

Answer 34

Answer: C

Question 35

The alternative pathway is also called the: A) Lectin pathway B) Properdin pathway C) Classical pathway D) Antibody pathway

Answer 35

B

Question 36

Which complement protein initiates the formation of the MAC? A) C3b B) C5b C) C6 D) C9

Answer 36

B

Question 37

The MAC creates a pore in the membrane of target cells, leading to: A) Phagocytosis B) Apoptosis C) Cell lysis D) Inflammation

Answer 37

Answer: C

Question 38

Which complement protein inserts into the membrane to form a pore? A) C6 B) C7 C) C8 D) C9

Answer 38

D

Question 39

What is the function of C5b in MAC formation? A) Cleaves C3 B) Initiates MAC assembly C) Activates immune cells D) Enhances inflammation

Answer 39

B

Question 40

The MAC is most effective against: A) Viruses B) Bacteria with thick peptidoglycan layers C) Gram-negative bacteria D) Fungi

Answer 40

C

Question 41

Which complement receptor is used by Epstein-Barr Virus (EBV) to infect B cells? A) CR1 B) CR2 C) CR3 D) CR4

Answer 41

Answer: B

Question 42

CR1 is found on which type of cells? A) B cells and T cells B) Platelets and red blood cells C) Only macrophages D) Neutrophils only

Answer 42

Answer: B

Question 43

The primary role of CR3 and CR4 is to: A) Activate B cells B) Facilitate phagocytosis C) Activate the alternative pathway D) Enhance inflammation

Answer 43

B

Question 44

Which receptor binds C3b-coated immune complexes for clearance? A) CR1 B) CR2 C) CR3 D) CR4

Answer 44

A

Question 45

The absence of complement receptors on white blood cells leads to: A) Overactivation of complement B) Impaired chemotaxis and phagocytosis C) Increased antibody production D) Resistance to infections

Answer 45

Answer: B

Question 46

Which deficiency is associated with Systemic Lupus Erythematosus (SLE)-like syndrome? A) C1 B) C2 C) C4 D) All of the above

Answer 46

Answer: D

Question 47

Which deficiency leads to an increased risk of Neisseria infections? A) C3 B) C5-C8 C) Factor H D) Factor B

Answer 47

Answer: B

Question 48

Deficiency of which complement component is associated with glomerulopathies? A) C1 B) C3 C) C9 D) Properdin

Answer 48

Answer: B

Question 49

Paroxysmal nocturnal hemoglobinuria (PNH) is caused by a deficiency in: A) C3 B) Factor H C) Decay-accelerating factor (DAF) D) C9

Answer 49

Answer: C

Question 50

Which monoclonal antibody can be used to treat complement-mediated disorders like PNH? A) Infliximab B) Rituximab C) Eculizumab D) Adalimumab

Answer 50

Answer: C