Question 1

Which of the following best describes the primary function of the complement system in the second line of defense?

Accepted Answer

It forms protein complexes that create holes in bacterial cell walls, leading to cell lysis.

Question 2

A patient is prescribed a broad-spectrum antibiotic, which reduces their beneficial gut bacteria. What is a likely consequence related to the first line of defense?

Accepted Answer

Decreased competitive exclusion, allowing pathogenic bacteria to proliferate.

Question 3

Which of the following is NOT a characteristic of the inflammatory response?

Accepted Answer

Decreased permeability of capillaries.

Question 4

Helper T-cells are crucial in the immune response because they:

Accepted Answer

Secrete cytokines that stimulate other immune cells, linking innate and adaptive immunity.

Question 5

Which antibody class is most abundant in blood and can cross the placenta to provide fetal immunity?

Accepted Answer

IgG

Question 6

A person with a genetic defect preventing the production of MHC proteins would most likely experience which immune system problem?

Accepted Answer

Failure to distinguish self from non-self, leading to impaired T-cell activation.

Question 7

Which process describes how phagocytes destroy bacteria?

Accepted Answer

They engulf bacteria into vesicles, which fuse with lysosomes for digestion.

Question 8

What is the main role of interferons in the immune response?

Accepted Answer

They stimulate nearby healthy cells to produce proteins that inhibit viral replication.

Question 9

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

Accepted Answer

It increases the metabolic rate of body cells, speeding up defense mechanisms and tissue repair.

Question 10

A patient receives a kidney transplant and begins to reject the organ. Which immune cells are primarily responsible for this response?

Accepted Answer

Cytotoxic T-cells recognizing foreign MHC proteins.

Question 11

Which of the following is a correct sequence of events in the activation of cytotoxic T-cells?

Accepted Answer

Antigen presentation by APC → Activation of CD8 T-cell → Clonal expansion → Attack on target cell

Question 12

Which of the following best describes the role of memory cells in adaptive immunity?

Accepted Answer

They store information about specific antigens for a faster response upon re-exposure.

Question 13

Which of the following is a function of IgA antibodies?

Accepted Answer

They neutralize infectious pathogens in mucous membranes and are present in breast milk.

Question 14

A mutation prevents the production of perforin in cytotoxic T-cells. What is the most likely consequence?

Accepted Answer

Impaired ability to lyse virus-infected or cancerous cells.

Question 15

Which of the following best explains why the skin is considered the most important physical barrier in the first line of defense?

Accepted Answer

Its keratinized structure, acidic pH, and antimicrobial secretions make it difficult for pathogens to penetrate.

Question 16

Which of the following is a direct effect of antibody binding to an antigen?

Accepted Answer

Agglutination, which reduces the number of infectious units to be dealt with.

Question 17

Which of the following best describes the role of antigen-presenting cells (APCs) in the immune response?

Accepted Answer

They engulf pathogens, process antigens, and present them on their surface with MHC molecules to activate T-cells.

Question 18

Which of the following is a function of suppressor T-cells?

Accepted Answer

They suppress the immune response once the antigen is neutralized, preventing autoimmunity.

Question 19

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

Accepted Answer

Urination physically flushes out microorganisms and the slightly acidic pH inhibits pathogen survival.

Question 20

A patient with a deficiency in helper T-cells would most likely experience which of the following?

Accepted Answer

Impaired activation of both B-cells and cytotoxic T-cells, leading to weakened adaptive immunity.

The Immune System: Lines of Defense

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