Question 1

Which of the following best describes a key difference between innate and adaptive immunity?

Accepted Answer

Innate immunity responds immediately to pathogens, while adaptive immunity takes days to develop.

Question 2

A patient is taking broad-spectrum antibiotics for a bacterial infection. After a week, they develop a yeast infection. Which mechanism best explains this outcome?

Accepted Answer

The antibiotics disrupted the normal microbiota, reducing competition and allowing opportunistic pathogens to overgrow.

Question 3

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

Accepted Answer

It generates immunological memory for faster future responses.

Question 4

A researcher observes that a certain bacterium is unable to establish infection in the stomach due to the acidic environment. Which innate immune component is primarily responsible for this defense?

Accepted Answer

Stomach acid (HCl)

Question 5

Which of the following best explains how phagocytes recognize pathogens during an innate immune response?

Accepted Answer

Phagocytes use pattern recognition receptors (PRRs) to bind to pathogen-associated molecular patterns (PAMPs).

Question 6

Which of the following is an example of a chemical barrier in innate immunity?

Accepted Answer

Lysozyme in tears

Question 7

A patient with a genetic defect in complement protein production is more susceptible to infections. Which role of complement proteins in innate immunity best explains this increased risk?

Accepted Answer

Complement proteins directly kill pathogens by forming membrane attack complexes.

Question 8

Which of the following scenarios best illustrates the concept of competitive exclusion by normal microbiota?

Accepted Answer

Normal microbiota occupy attachment sites and consume nutrients, preventing pathogens from establishing.

Question 9

Which of the following is a correct sequence of events during phagocytosis by a macrophage?

Accepted Answer

Recognition → Engulfment → Phagosome formation → Fusion with lysosome → Destruction

Question 10

A patient with a severe burn loses a large area of skin. Which aspect of innate immunity is most compromised in this patient?

Accepted Answer

Physical barrier function of the skin

Question 11

Which of the following is a function of dendritic cells in innate immunity that also links to adaptive immunity?

Accepted Answer

They present antigens to T cells, initiating adaptive immune responses.

Question 12

A patient undergoing chemotherapy develops an infection with a normally harmless gut bacterium. Which factor most likely contributed to this infection?

Accepted Answer

Suppression of the immune system, allowing normal microbiota to become opportunistic pathogens

Question 13

Which of the following best describes the inflammatory response in innate immunity?

Accepted Answer

It involves redness, heat, swelling, and pain at the site of infection.

Question 14

Which of the following is NOT a way that normal microbiota protect against pathogens?

Accepted Answer

Directly phagocytosing invading bacteria

Question 15

A laboratory experiment shows that lysozyme can break down bacterial cell walls. Which type of molecule is lysozyme most likely to target?

Accepted Answer

Peptidoglycan

Question 16

Which of the following best explains why adaptive immunity is slower to respond than innate immunity upon first exposure to a pathogen?

Accepted Answer

Adaptive immunity requires clonal selection and expansion of specific lymphocytes.

Question 17

A patient develops a urinary tract infection after E. coli from the gut enters the urinary tract. This is an example of which process?

Accepted Answer

Introduction of normal microbiota to an unusual site, leading to opportunistic infection

Question 18

Which of the following is a soluble factor involved in innate immunity?

Accepted Answer

Complement proteins

Question 19

A scientist is studying the effect of antimicrobial peptides on bacteria. Which mechanism do these peptides most likely use to inhibit bacterial growth?

Accepted Answer

Disrupting microbial membranes

Question 20

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

Accepted Answer

Cytokines are signaling molecules that help coordinate immune responses.

Innate Immunity: The Body’s First Line of Defense

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