Question 1

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

Accepted Answer

Innate immunity is rapid and nonspecific, while adaptive immunity is slower, highly specific, and generates memory.

Question 2

A patient with a genetic defect in the formation of tight junctions between epithelial cells would most likely experience which of the following?

Accepted Answer

Increased susceptibility to microbial invasion due to compromised physical barriers.

Question 3

Which of the following is the correct sequence of events during phagocytosis?

Accepted Answer

Chemotaxis → Adherence → Ingestion → Digestion → Exocytosis

Question 4

A researcher is studying a molecule that disrupts bacterial membranes and also recruits immune cells by triggering cytokine release. This molecule is most likely:

Accepted Answer

An antimicrobial peptide (AMP)

Question 5

Which of the following best explains why opsonization is especially important for clearing encapsulated bacteria?

Accepted Answer

Encapsulated bacteria resist direct phagocytosis, but opsonins like C3b enhance their recognition and uptake by phagocytes.

Question 6

A patient with impaired cilia function in the respiratory tract is at increased risk for infection because:

Accepted Answer

The mucociliary escalator is less effective at clearing trapped microbes and debris.

Question 7

Which of the following statements about the complement system is correct?

Accepted Answer

The classical pathway is initiated when an antibody binds to a pathogen, leading to C1 activation.

Question 8

A laboratory test shows a patient has high levels of C-reactive protein (CRP). What does this most likely indicate?

Accepted Answer

The patient is experiencing inflammation, and CRP is acting as an opsonin and enhancing complement activation.

Question 9

Which of the following best describes the role of defensins in the innate immune system?

Accepted Answer

They are small, positively charged peptides that disrupt microbial membranes and help shape early immune responses.

Question 10

A viral infection triggers the production of type I interferons (IFN-α and IFN-β). What is the primary effect of these interferons?

Accepted Answer

They induce an antiviral state in neighboring cells.

Question 11

Which of the following is a correct example of a mechanical flushing action that helps prevent microbial attachment?

Accepted Answer

Urine flow in the urinary tract

Question 12

A patient is unable to produce lysozyme in their tears and saliva. Which of the following would most likely result?

Accepted Answer

Increased susceptibility to bacterial infections due to reduced breakdown of peptidoglycan.

Question 13

Which of the following best describes the function of natural killer (NK) cells in the innate immune system?

Accepted Answer

They kill virus-infected or tumor cells by detecting missing self and releasing perforin and granzymes.

Question 14

Which of the following is NOT a function of cytokines in the innate immune response?

Accepted Answer

Directly lysing bacterial cell walls

Question 15

A mutation prevents the formation of the phagolysosome in macrophages. Which step of phagocytosis is directly impaired?

Accepted Answer

Digestion of the engulfed microbe

Question 16

Which of the following best explains why inflammation can be both protective and damaging?

Accepted Answer

Controlled inflammation helps clear infection and repair tissue, but excessive or chronic inflammation can damage host tissues.

Question 17

Which of the following is the correct order of the inflammatory sequence in response to infection?

Accepted Answer

Trigger (PAMPs/DAMPs) → Sensor (PRRs) → Signal (cytokines/chemokines) → Response (immune cell recruitment) → Resolution (pathogen clearance/tissue repair)

Question 18

A patient is exposed to a new bacterial pathogen. Which of the following components of the innate immune system is most likely to recognize conserved microbial structures such as flagella or cell wall components?

Accepted Answer

Pattern-recognition receptors (PRRs)

Question 19

Which of the following best describes the function of bacteriocins in the human gut?

Accepted Answer

They are antimicrobial peptides produced by bacteria to kill closely related bacterial species, helping beneficial microbes compete.

Question 20

A patient with a deficiency in C3 convertase formation would have impaired function in which of the following processes?

Accepted Answer

Opsonization, inflammation, and formation of the membrane attack complex

Innate Immunity: Structure and Function in Host Defense

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