Question 1

Which of the following best describes an epitope?

Accepted Answer

A site on an antigen where an antibody binds

Question 2

A patient is exposed to a novel virus for the first time. Which immune response is primarily responsible for the initial defense against this virus?

Accepted Answer

Primary adaptive response

Question 3

Which of the following statements about antigens is correct?

Accepted Answer

Antigens can be proteins or large polysaccharides that trigger an antibody response

Question 4

What is the main function of the variable region of an antibody?

Accepted Answer

To bind specifically to an epitope on an antigen

Question 5

Which process is responsible for generating the diversity of antibody variable regions in B cells?

Accepted Answer

DNA recombination (VDJ recombination)

Question 6

A mutation in the gene encoding the MHC I molecule would most directly impair which immune function?

Accepted Answer

Presentation of endogenous antigens to cytotoxic T cells

Question 7

Which of the following best explains why Trypanosoma brucei can evade the host antibody response?

Accepted Answer

It frequently changes its surface glycoproteins using a large repertoire of VSG genes

Question 8

During the primary immune response, which antibody class is produced first?

Accepted Answer

IgM

Question 9

Which of the following is a correct sequence of events for antigen processing and presentation by a B cell?

Accepted Answer

Antigen binds to IgM on B cell surface → Endocytosis → Antigen degraded → Peptides presented on MHC II

Question 10

Which of the following best describes the role of cytotoxic T cells (Tc cells) in the immune response?

Accepted Answer

They recognize antigens presented by MHC I and induce cytolysis of infected cells

Question 11

A patient receives a flu vaccine containing inactivated virus. Which type of adaptive immune response is primarily stimulated?

Accepted Answer

Humoral (antibody-mediated) response (Th2)

Question 12

Which of the following is a real-world example of antigenic shift?

Accepted Answer

A human influenza virus acquiring bird influenza virus genes, resulting in a new subtype

Question 13

Which of the following best explains why the immune system does not attack the body's own cells under normal conditions?

Accepted Answer

T cells are selected in the thymus for tolerance of self-antigens

Question 14

A patient is infected with a virus that mutates rapidly in its hemagglutinin (HA) gene. Which immune evasion mechanism is this an example of?

Accepted Answer

Antigenic drift

Question 15

Which of the following best describes the function of MHC II molecules?

Accepted Answer

Present exogenous antigens to helper T cells

Question 16

A researcher is studying a new pathogen that is able to avoid detection by the host's immune system. Which of the following strategies would most likely allow the pathogen to evade antibody-mediated immunity?

Accepted Answer

Frequently changing its surface antigens

Question 17

Which of the following best explains the process of clonal selection in B cells?

Accepted Answer

B cells with receptors specific to an encountered antigen proliferate and differentiate into plasma cells and memory cells

Question 18

Which of the following equations best represents the diversity of antibodies generated by VDJ recombination, given $$V$$ variable, $$D$$ diversity, and $$J$$ joining gene segments?

Accepted Answer

$$N = V 	imes D 	imes J$$

Question 19

A patient is exposed to tetanus toxoid for the first time. Which of the following best describes the expected antibody response over the first 15 days?

Accepted Answer

A slow increase in IgM, followed by a gradual increase in IgG

Question 20

Which of the following is a function of interleukin-2 (IL-2) in the immune response?

Accepted Answer

Stimulates proliferation of T and B cells

Host Defenses and Adaptive Immunity: Antibodies, Antigens, and the Immune System

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