Question 1

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

Accepted Answer

It acts as a physical barrier and secretes antimicrobial chemicals such as lysozyme and sebum.

Question 2

A patient with a genetic defect in collagen synthesis is more susceptible to infections. Which component of the first line of defense is most directly affected?

Accepted Answer

Dermis

Question 3

Which of the following is a function of the resident microbiome in host defense?

Accepted Answer

It competes with pathogens for resources, making it harder for them to establish infection.

Question 4

A laboratory test shows increased levels of eosinophils in a patient's blood. This finding is most consistent with which type of infection?

Accepted Answer

Helminth (parasitic worm) infection

Question 5

Which of the following best describes the process of phagocytic killing by macrophages?

Accepted Answer

It is divided into six stages, including chemotaxis, adherence, ingestion, maturation, killing, and elimination.

Question 6

Which of the following is NOT a function of Toll-like receptors (TLRs) in the innate immune response?

Accepted Answer

Direct phagocytosis of pathogens

Question 7

A patient develops a fever after a bacterial infection. Which of the following best explains the physiological mechanism behind this response?

Accepted Answer

Pyrogens trigger the hypothalamus to increase the body's temperature.

Question 8

Which pathway of complement activation is initiated by the binding of antibodies to antigens?

Accepted Answer

Classical pathway

Question 9

During acute inflammation, which of the following mediators is NOT directly involved in promoting vasodilation?

Accepted Answer

Lysozyme

Question 10

A patient with chronic inflammation is at increased risk for which of the following outcomes?

Accepted Answer

Long-lasting tissue damage that can cause disease

Question 11

Which of the following best describes the role of natural killer (NK) cells in the second line of defense?

Accepted Answer

They secrete toxins to kill virus-infected or tumor cells.

Question 12

Which of the following is a correct sequence of events during the acute inflammatory response?

Accepted Answer

Vasodilation → Migration of phagocytes → Tissue repair

Question 13

Which of the following is a characteristic of the alternative pathway of complement activation?

Accepted Answer

It is activated by pathogen surfaces without the need for antibodies.

Question 14

A patient with a deficiency in lysozyme production would be most susceptible to infections in which of the following areas?

Accepted Answer

Tears and mucous membranes

Question 15

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

Accepted Answer

It increases the rate of phagocytosis and inhibits the growth of some pathogens.

Question 16

Which of the following is a correct statement about the role of interferons in host defense?

Accepted Answer

Type I interferons are produced in response to viral infections and help protect neighboring cells.

Question 17

A patient is exposed to a bacterial toxin that acts as a pyrogen. Which equation best represents the relationship between body temperature ($$T$$), pyrogen concentration ($$P$$), and hypothalamic set point ($$S$$)?

Accepted Answer

$$T = S + kP$$, where $$k is a $$proportionality constant

Question 18

Which of the following best describes the function of complement proteins in the immune response?

Accepted Answer

They form membrane attack complexes that lyse pathogens.

Question 19

A patient with a deficiency in neutrophil function would have difficulty with which of the following?

Accepted Answer

Producing chemicals that kill nearby invaders

Question 20

Which of the following is a correct statement about the role of PAMPs (pathogen-associated molecular patterns) in the immune response?

Accepted Answer

PAMPs are recognized by TLRs, leading to secretion of inflammatory mediators and stimulation of the adaptive immune response.

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

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