Immunology #2: Innate Immunity

1.

C3 is normally at low concentrations in the body. Therefore, large quantities must be produced before C3b formation and binding to the pathogen

A.

True
B.

False

Correct Answer
B. False

Explanation
In a health person, C3 is always in high concentrations in the body. However, mannose-binding lectin and C-reactive protein increase levels during inflammation explaining their later role in the response to infection.

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2.

All pathways come to the same end, the cleavage of the C3 into C3b and C3a

A.

True
B.

False

Correct Answer
A. True

Explanation
This statement is true because regardless of the pathway (classical, lectin, or alternative) that activates the complement system, they all converge at the same point, which is the cleavage of C3 into C3b and C3a. This cleavage is an essential step in the complement cascade, leading to the opsonization of pathogens, recruitment of immune cells, and inflammation. Therefore, regardless of the initiating pathway, the end result is the same.

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3.

Which of the following represents the correct order of events in the formation of C3b, from first to last?

A.

B binds to iC3, B cleaves with to form the iC3Bb complex, D binds then leaves, another C3 binds and is cleaved into C3a and C3b
B.

B binds to iC3, D binds then leaves, B cleaves with to form the iC3Bb complex, another C3 binds and is cleaved into C3a
C.

D binds then leaves, B binds to iC3, B cleaves with to form the iC3Bb complex, another C3 binds and is cleaved into C3a

Correct Answer
B. B binds to iC3, D binds then leaves, B cleaves with to form the iC3Bb complex, another C3 binds and is cleaved into C3a

4.

Another name for the alternative C3 convertase enzyme is

Correct Answer
C3bBb

Explanation
The alternative C3 convertase enzyme is also known as C3bBb.

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5.

Examples of anaphylatoxins include (check all that apply)

A.

C3b
B.

C3a
C.

C5b
D.

C5a

Correct Answer(s)
B. C3a
D. C5a

Explanation
Anaphylatoxins are small proteins that are generated during the activation of the complement system. They play a crucial role in inflammation and immune response. C3a and C5a are both examples of anaphylatoxins. They are produced when the complement protein C3 and C5 are cleaved, respectively. These anaphylatoxins can induce the release of histamine from mast cells, leading to vasodilation, increased vascular permeability, and recruitment of immune cells to the site of inflammation. Therefore, C3a and C5a are correct answers for examples of anaphylatoxins. C3b and C5b, on the other hand, are not anaphylatoxins but rather components of the complement system involved in opsonization and formation of the membrane attack complex, respectively.

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1

6.

Which of the following statements correctly describes the actions of Toll-Like Receptors 3 & 4?

A.

TLR-3 works within cell recognizing the double-stranded RNA of viruses; TLR-4, on the outside of the cell recognizes LPS on gram-negative bacteria
B.

TLR-3 on the outside of the cell recognizes LPS on gram-negative bacteria; TLR-4 works within cell recognizing the double-stranded RNA of viruses

Correct Answer
A. TLR-3 works within cell recognizing the double-stranded RNA of viruses; TLR-4, on the outside of the cell recognizes LPS on gram-negative bacteria

Explanation
TLR-3 is located within the cell and is responsible for recognizing the double-stranded RNA of viruses. On the other hand, TLR-4 is located on the outside of the cell and is responsible for recognizing LPS (lipopolysaccharide) on gram-negative bacteria.

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7.

Which of the following is NOT an action of the Type 1 Interferon alpha and beta

A.

Increase resistance to viral replication
B.

Decrease resistance to viral replication
C.

Increase NK cell killing
D.

Create viral ligands to work on NK cell receptors to increase expression of the ligands

Correct Answer
B. Decrease resistance to viral replication

Explanation
Type 1 interferon alpha and beta are known to have antiviral effects. They are released in response to viral infections and play a crucial role in inhibiting viral replication. They increase resistance to viral replication by inducing the expression of various antiviral proteins within infected cells. Additionally, they enhance the activity of natural killer (NK) cells, which are important in killing virus-infected cells. Therefore, the action of decreasing resistance to viral replication is not associated with Type 1 interferon alpha and beta.

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8.

An antibody is an example of an opsonin

A.

True
B.

False

Correct Answer
A. True

Explanation
An opsonin is a substance that enhances the process of phagocytosis by marking pathogens or other foreign particles for destruction by immune cells. Antibodies, produced by the immune system in response to an infection or vaccination, can act as opsonins by binding to pathogens and facilitating their recognition and engulfment by phagocytes. Therefore, an antibody is indeed an example of an opsonin.

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