This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Diverse Functions of Complement”.
1. As an essential component of the immune system, complement is _________
a) A first line of defense
b) A second line of defense
c) An anatomical barrier
d) Inhibition mechanism
View Answer
Explanation: Complement is an essential component of both innate and adaptive immunity. When it comes to innate immunity, this acts as a first line of defense against pathogens.
2. When does a complement get activated?
a) When hydrolysis occurs in the body
b) When a pathogen attacks
c) When there is an over expression of markers
d) When there is uncontrolled growth of cells
View Answer
Explanation: The complement pathways are activated only then when a pathogen has entered the body. As it is activated, it forms MAC and helps the phagocyte to degrade the pathogen.
3. Which of the following pathways are activated when a pathogen specific antibody is present in the host?
a) Classical pathway
b) Alternative pathway
c) MB-lectin pathway
d) Both alternative and MB-lectin pathways
View Answer
Explanation: The classical pathway can be very specific. It gets activated when there is a pathogen specific antibody present in the host.
4. Complement activation ultimately leads to _________
a) Convertase formation
b) MAC formation
c) C9 polymerisation
d) Increase in deposition of C3b
View Answer
Explanation: Complement pathway ultimately leads to the formation of MAC, Membrane Attack Complex. This invades the surface of pathogen.
5. Which of the following cleaves C3 into iC3b and C3f?
a) C3
b) Factor I
c) Factor B
d) Factor D
View Answer
Explanation: Factor I cleaves C3 into iC3b and C3f. It also further cleaves iC3b into C3c and C3dg. Serum proteases cleave C3dg into C3g and c3d.
6. What cleaves C3dg into C3d and C3g?
a) Factor I
b) Factor B
c) Factor D
d) Serum proteases
View Answer
Explanation: Factor I cleaves C3 into iC3b and C3f. It also further cleaves iC3b into C3c and C3dg. Serum proteases cleave C3dg into C3g and c3d.
7. Which of the following complement receptors (CRs) help in mediating the complement-dependent phagocytosis?
a) CR3 and CR2
b) CR3 and CR4
c) CR2 and CR5
d) CR4 and CR5
View Answer
Explanation: The complement receptors CR3 and CR4 help in mediating the complement-dependent phagocytosis. Both of these receptors belong to 02 integrin family.
8. C5a is a _______ agent to neutrophils, basophils and monocytes.
a) Phagocytic
b) Chemotactic
c) Cytotoxic
d) Regulating
View Answer
Explanation: In addition to causing degranulation of basophils and mast cells, C5a is also a strong chemotactic agent for the rest of the cells as it primes these phagocytic cells.
9. Complement mechanism also contributes to induction of inflammatory response. True/False?
a) True
b) False
View Answer
Explanation: The complement mechanism contributes to induction of inflammatory responses via C3a and C5a fragments. These are called as anaphylatoxins and mediate in inflammation.
10. Is clearing out the dead and dying cells a function of complement. True/False?
a) False
b) True
View Answer
Explanation: Complement is not just for forming the MAC, but also to clear out the immune complexes and dead and dying cells from the body.
11. Which of the following antibodies recognize neoepitopes?
a) IgD
b) IgM
c) IgA
d) IgE
View Answer
Explanation: Neoepitopes are expressed by the apoptotic cells on their surface. These are recognized by freely circulating IgM antibodies, leading to complement opsonization.
Sanfoundry Global Education & Learning Series – Immunology.
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