Question 1

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

Accepted Answer

It acts as a physical barrier with tightly packed cells and keratin, preventing microbial entry and desiccation.

Question 2

A patient with a genetic defect in Toll-Like Receptors (TLRs) would most likely have difficulty with which aspect of innate immunity?

Accepted Answer

Recognizing and binding to pathogen-associated molecular patterns (PAMPs) on microbes.

Question 3

Which of the following is a chemical factor of the first line of innate defense that contributes to the skin’s antimicrobial properties?

Accepted Answer

Sebum, which lowers skin pH to 3–5

Question 4

The ciliary escalator is an important defense mechanism in the respiratory tract. What is its primary function?

Accepted Answer

To transport microbes trapped in mucus away from the lungs.

Question 5

Which of the following best explains why the human microbiome is considered a part of the first line of innate defense?

Accepted Answer

It competes with pathogens for nutrients and attachment sites, preventing colonization.

Question 6

A cut on the skin introduces bacteria into the tissue. Which sequence best describes the events of the acute inflammatory response?

Accepted Answer

Release of mediators (histamine, kinins), vasodilation, phagocyte migration, tissue repair

Question 7

Which of the following is NOT a cardinal sign of inflammation?

Accepted Answer

Pallor

Question 8

Which of the following best describes the function of C3b in the complement cascade?

Accepted Answer

Acts as an opsonin, enhancing phagocytosis of microbes

Question 9

A patient is unable to produce sufficient gastric acid. Which aspect of their innate immunity is most compromised?

Accepted Answer

Chemical barrier in the stomach, increasing susceptibility to ingested pathogens

Question 10

Which pathway of complement activation is triggered by antibody binding to a pathogen?

Accepted Answer

Classical pathway

Question 11

Which of the following best describes the role of Pattern Recognition Receptors (PRRs) on phagocytes?

Accepted Answer

They recognize common molecular patterns found on pathogens, such as LPS and peptidoglycan.

Question 12

Which of the following is a correct statement about the membrane attack complex (MAC) formed during complement activation?

Accepted Answer

It creates pores in bacterial membranes, leading to cell lysis.

Question 13

Which of the following is a real-life example of competitive exclusion by the human microbiome?

Accepted Answer

Staphylococcus epidermidis on the skin outcompetes pathogenic Staphylococcus aureus for nutrients and space.

Question 14

Which of the following best explains why a deficiency in C3 protein would result in increased susceptibility to bacterial infections?

Accepted Answer

C3 is central to all complement activation pathways and is necessary for opsonization, inflammation, and MAC formation.

Question 15

Which of the following is a function of lysozyme in innate immunity?

Accepted Answer

Hydrolyzing peptidoglycan in bacterial cell walls, leading to cell lysis

Question 16

A patient with a severe burn loses large areas of skin. Which aspect of their innate immunity is most compromised?

Accepted Answer

Physical barrier to microbial entry

Question 17

Which of the following best describes the role of neutrophils in the inflammatory response?

Accepted Answer

They are attracted to sites of infection by chemotactic mediators and perform phagocytosis.

Question 18

Which of the following is a correct sequence of events in the classical complement pathway?

Accepted Answer

C1 activation → C2 and C4 cleavage → C3 convertase formation → C3 cleavage → C5 cleavage → MAC formation

Question 19

Which of the following best explains why the lacrimal apparatus is considered a first line of defense?

Accepted Answer

It continuously flushes microbes from the surface of the eye into the nasal cavity.

Innate Immunity: The Human Immune Response – First and Second Line Defenses

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