Question 1

Which of the following best describes the main difference between the third line of defense (adaptive immunity) and the first two lines of defense in the immune system?

Accepted Answer

It is highly specific and generates memory cells for future responses.

Question 2

Which of the following statements about antigens, immunogens, and epitopes is correct?

Accepted Answer

An immunogen is an antigen that provokes an immune response, and an epitope is the specific part of the antigen recognized by lymphocytes.

Question 3

Which of the following is NOT a characteristic of adaptive immunity?

Accepted Answer

Immediate response without prior exposure

Question 4

Which of the following best describes the role of the major histocompatibility complex (MHC) in the immune response?

Accepted Answer

It encodes cell surface markers that help the immune system distinguish self from non-self.

Question 5

Which class of MHC molecules is found on all nucleated cells and is essential for presenting endogenous antigens to cytotoxic T cells?

Accepted Answer

MHC class I

Question 6

A patient receives antibodies from a donor after exposure to a toxin. Which type of immunity is this an example of?

Accepted Answer

Artificial passive immunity

Question 7

Which of the following best explains why the immune system does not normally attack the body’s own cells?

Accepted Answer

Clonal deletion removes self-reactive lymphocytes during development.

Question 8

Which of the following is a function of helper T cells (CD4+)?

Accepted Answer

Activate macrophages and assist B-cell processes

Question 9

Which of the following is NOT a typical target for cytotoxic T cells (CD8+)?

Accepted Answer

Bacteria in the bloodstream

Question 10

Which of the following best describes the process of clonal selection?

Accepted Answer

The activation and proliferation of a lymphocyte with a receptor specific for a presented antigen

Question 11

Which of the following is a characteristic of a good immunogen?

Accepted Answer

High molecular complexity and foreignness

Question 12

Which of the following cells can act as antigen-presenting cells (APCs)?

Accepted Answer

Macrophages, dendritic cells, and B cells

Question 13

Which immunoglobulin is most prevalent in serum and is responsible for long-term immunity?

Accepted Answer

IgG

Question 14

A child receives antibodies from breast milk. What type of immunity is this?

Accepted Answer

Natural passive immunity

Question 15

Which of the following best describes the difference between the primary and secondary immune response to an antigen?

Accepted Answer

The secondary response is faster and produces more antibodies due to memory cells.

Question 16

Which of the following vaccine types uses a weakened but live form of the pathogen to stimulate immunity?

Accepted Answer

Live, attenuated vaccine

Question 17

Which of the following best explains why mRNA vaccines (such as Pfizer & Moderna COVID-19 vaccines) are effective?

Accepted Answer

They deliver mRNA encoding a viral protein, which is then expressed and presented to the immune system.

Question 18

Which of the following is a function of the Fc region of an antibody?

Accepted Answer

Binding to receptors on phagocytes and other immune cells

Question 19

Which immunoglobulin is primarily responsible for mucosal immunity and is found in secretions such as saliva and breast milk?

Accepted Answer

IgA

Question 20

A patient is exposed to a nonpathogenic microbe that shares epitopes with a dangerous pathogen, resulting in immunity to the pathogen. Which concept does this illustrate?

Accepted Answer

Cross-reactive memory

Adaptive Immunity and Immunization: The Third Line of Host Defense

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