This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Major Pathways of Complement Activation”.
1. In alternative pathway, the Bb fragment from C3b and Factor B complex forms a complex with _______
a) C3a
b) C3b
c) Factor B
d) C3
View Answer
Explanation: The Bb fragment forms complex with c3b again to form C3bBb BAR. This resembles C3 convertase as in classical pathway’s C4b2a.
2. Which of the following convertases does the C3bBb BAR resemble?
a) C3 convertase
b) C4 convertase
c) C2 convertase
d) C5 convertase
View Answer
Explanation: C3bBb BAR resembles C3 convertase as in classical pathway’s C4b2a BAR. It catalyzes the proteolytic cleavage of C3 protein into C3a and C3b.
3. In alternative pathway, the C3bBb BAR forms complex with _______
a) C3a
b) C3b
c) Factor B
d) C5
View Answer
Explanation: The C3bBb BAR further forms complex with C3b to form C3bBb3b BAR. This C3bBb3b BAR cleaves C5 complement protein.
4. Which of the following convertases does the C3bBb3b BAR resemble?
a) C3 convertase
b) C4 convertase
c) C2 convertase
d) C5 convertase
View Answer
Explanation: C3bBb3b BAR resembles C5 convertase as in classical pathway’s C4b2a3b BAR. It catalyzes the proteolytic cleavage of C5 protein into C5a and C5b.
5. Both in Classical and Alternative pathways, which of the following complex formation chain is correct after the C5 convertase formation?
a) C5 convertase → C5b → C6 → C7 → C8 → C9 → MAC
b) C5 convertase → C5a → C8 → C7 → C6 → C9 → MAC
c) C5 convertase → C5b → C6 → C8 → C8 → C7 → MAC
d) C5 convertase → C5a → C6 → C9 → C8 → C7 → MAC
View Answer
Explanation: C5 convertase → C5b → C6 → C7 → C8 → C9 → MAC is the right chain of complex formation ultimately leading to Membrane Attack Complex (MAC) formation.
6. C3bBb BAR and C3bBb3b BAR are unstable if they don’t bind with_______
a) Factor B
b) Factor D
c) C3b
d) Properdin
View Answer
Explanation: Properdin is one of the proteins involved in alternative pathway. It stabilizes the C3 and C5 convertases of this pathway by increasing their half-lives.
7. In the MB-lectin pathway, MASP-1 resembles _______ of classical pathway.
a) C1r BAR
b) C1s BAR
c) C3 convertase
d) C5 convertase
View Answer
Explanation: MASP-1, MBL Associated Serine Protease-1, resembles C1r BAR. It plays a role by recognizing pathogens through patterns of sugar moieties and neutralizing them.
8. In the MB-lectin pathway, MASP-2 resembles _______ of classical pathway.
a) C1r BAR
b) C1s BAR
c) C3 convertase
d) C5 convertase
View Answer
Explanation: MASP-2, MBL Associated Serine Protease-2, resembles C1s BAR. It performs the same function as C1s BAR like in classical pathway.
9. In the MB-lectin pathway, sialic acid regulates the production of which of the following?
a) C3b
b) C3
c) C3 convertase
d) C5 convertase
View Answer
Explanation: Sialic acid regulates the production of C3b in the MB-lectin pathway. Sialic acid is high in our body and less in the pathogen.
10. In the MB-lectin pathway, C3b acts as an?
a) C3 convertase
b) C5 convertase
c) Opsonin
d) Phagolysosome
View Answer
Explanation: C3b acts as an opsonin. It enhances the process of an entity to be phagocytosed. It can specifically bind to the complement receptor 1 (CR1) present on macrophage.
Sanfoundry Global Education & Learning Series – Immunology.
To practice all areas of Immunology, here is complete set of 1000+ Multiple Choice Questions and Answers.
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