Question 1

Which of the following best describes the role of the skin in the body's first line of defense against pathogens?

Accepted Answer

It acts as a physical barrier with tightly packed cells, secretes antimicrobial substances, and sheds microorganisms with dead skin cells.

Question 2

A patient presents with an abnormally high number of eosinophils in their blood. Which of the following is the most likely explanation for this finding?

Accepted Answer

The patient has a helminth infestation or an allergic reaction.

Question 3

Which of the following mechanisms is NOT a way the normal microbiome protects against pathogens?

Accepted Answer

Directly phagocytizing invading bacteria.

Question 4

During phagocytosis, what is the correct sequence of events from initial contact to elimination of a pathogen?

Accepted Answer

Chemotaxis → Adhesion → Ingestion → Phagosome maturation and microbial killing → Elimination

Question 5

Which of the following statements about complement activation is correct?

Accepted Answer

Complement activation can occur via the classical, alternative, or lectin pathways, all leading to the formation of membrane attack complexes (MACs).

Question 6

A laboratory test shows a patient’s plasma contains high levels of transferrin and ferritin. What is the primary defensive function of these proteins?

Accepted Answer

They sequester iron, making it unavailable to microorganisms.

Question 7

Which of the following best explains why fever can be beneficial during an infection?

Accepted Answer

Fever enhances the effects of interferons, inhibits the growth of some microorganisms, and may improve phagocyte performance.

Question 8

A researcher is studying a protein that recognizes pathogen-associated molecular patterns (PAMPs) on the surface of bacteria and viruses. This protein is embedded in the cytoplasmic membrane of phagocytic cells. What is this protein most likely to be?

Accepted Answer

A Toll-like receptor (TLR)

Question 9

Which of the following is a correct description of the process of opsonization?

Accepted Answer

The coating of pathogens with molecules such as antibodies or complement proteins to enhance phagocytosis.

Question 10

A patient with a genetic defect in the production of lysozyme would be most susceptible to which of the following?

Accepted Answer

Increased risk of bacterial infections due to impaired breakdown of bacterial cell walls

Question 11

Which of the following is a function of natural killer (NK) cells in innate immunity?

Accepted Answer

They secrete toxins onto the surfaces of virally infected cells and tumor cells, sparing normal body cells.

Question 12

A patient is given a probiotic supplement after a course of antibiotics. What is the most likely intended effect of this treatment?

Accepted Answer

To rebalance the microbiome and help prevent or treat infection by restoring competitive inhibition.

Question 13

Which of the following best describes the role of defensins in innate immunity?

Accepted Answer

Defensins are antimicrobial peptides that can punch holes in microbial membranes, interrupt internal signaling, or act as chemotactic factors.

Question 14

A patient with a chronic wound is found to have significant scar tissue formation. Which of the following best explains why this tissue is less functional than the original tissue?

Accepted Answer

Scar tissue is formed by fibroblasts, which do not restore the original function of the tissue.

Question 15

Which of the following is a correct statement about the difference between plasma and serum?

Accepted Answer

Plasma contains clotting factors, while serum is plasma without clotting factors.

Question 16

A scientist is studying the effects of a new drug that inhibits the function of NOD proteins. Which of the following immune responses would most likely be impaired?

Accepted Answer

Recognition of PAMPs in the cytosol and triggering of apoptosis and inflammation.

Question 17

Which of the following best describes the process of diapedesis?

Accepted Answer

The movement of leukocytes out of the bloodstream by squeezing between endothelial cells to reach sites of infection.

Question 18

A patient with a fever has a body temperature of $$39^\circ \mathrm{C}. $$Which of the following physiological responses is most likely occurring to raise the body temperature?

Accepted Answer

Shivering, reduced sweating, and vasoconstriction of skin blood vessels.

Question 19

Which of the following is a correct statement about the function of interferons in innate immunity?

Accepted Answer

Interferons are proteins released by host cells that nonspecifically inhibit the spread of viral infections by triggering the production of antiviral proteins in neighboring cells.

Innate Immunity: The Body’s First and Second Lines of Defense

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