Question 1

Which of the following best describes the primary function of the skin as a barrier in host resistance to viral infections?

Accepted Answer

It acts as a physical and chemical barrier, preventing the entry of viruses, bacteria, and toxins into the body.

Question 2

Interferons play a crucial role in the innate immune response to viral infections. Which of the following is NOT a direct effect of interferon signaling?

Accepted Answer

Direct lysis of viral particles in the bloodstream.

Question 3

Which of the following best explains the role of interferon-stimulated genes (ISGs) in establishing an antiviral state?

Accepted Answer

ISGs encode proteins that interfere with various stages of the viral life cycle, such as degrading viral RNA and inhibiting viral protein synthesis.

Question 4

Natural Killer (NK) cells are part of the innate immune system. Which mechanism do they use to destroy virus-infected cells?

Accepted Answer

Release of perforin and granzymes to induce apoptosis in infected cells.

Question 5

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) involves which of the following steps?

Accepted Answer

NK cells recognize and bind to antibody-coated infected cells, then release cytotoxic molecules to induce apoptosis.

Question 6

Which of the following best describes the function of antigen-presenting cells (APCs) in the immune response to viral infection?

Accepted Answer

APCs ingest viruses, process them, and present viral peptides on MHC molecules to activate T cells.

Question 7

During a viral infection, which of the following best explains the time course of the immune response as shown in the provided graph?

Accepted Answer

Innate defenses such as interferons and NK cells act rapidly, while specific antibody responses develop more slowly over days to weeks.

Question 8

Which of the following is the most crucial mechanism by which antibodies halt the viral life cycle?

Accepted Answer

Neutralization, where antibodies bind to viral antigens and prevent the virus from entering host cells.

Question 9

Opsonization is a process that enhances the clearance of viruses from the body. Which statement best describes this process?

Accepted Answer

Antibodies coat viral particles, marking them for phagocytosis by cells such as macrophages.

Question 10

Cytotoxic T cells (CD8+) recognize and kill infected cells by which of the following mechanisms?

Accepted Answer

Binding to viral antigens presented on MHC class I molecules and releasing perforin and granzymes to induce apoptosis.

Question 11

Helper T cells (CD4+) play a central role in coordinating the adaptive immune response. Which of the following is NOT a function of helper T cells?

Accepted Answer

Directly killing virus-infected cells using perforin.

Question 12

Which of the following best distinguishes host resistance from host tolerance in the context of viral infections?

Accepted Answer

Resistance reduces the viral burden, while tolerance minimizes tissue damage without necessarily reducing viral load.

Question 13

A patient with a genetic defect in MHC class I molecules would most likely have impaired function in which immune cell type?

Accepted Answer

Cytotoxic T cells (CD8+)

Question 14

Which of the following equations best represents the relationship between the rate of viral clearance ($$C$$), the number of cytotoxic T cells ($$T$$), and the efficiency of apoptosis induction ($$E$$)?

Accepted Answer

$$C = T 	imes E$$

Question 15

A patient is exposed to a virus for the second time. Which of the following best explains why the immune response is faster and more robust than during the first exposure?

Accepted Answer

Immunological memory from memory B and T cells allows for rapid and enhanced response upon re-exposure.

Question 16

Which of the following factors does NOT directly influence an individual's resistance to viral infection?

Accepted Answer

The color of the individual's skin.

Question 17

In the context of viral evolution and host resistance, what is meant by the term 'evolutionary arms race'?

Accepted Answer

Continuous adaptation of both host defenses and viral evasion strategies over time.

Question 18

Which of the following best describes the process of phagocytosis as it relates to viral clearance?

Accepted Answer

Phagocytic cells engulf and digest antibody-coated viral particles, enhancing viral clearance from the body.

Question 19

A patient with chronic hepatitis C infection develops significant liver damage. Which of the following best explains the immunopathology observed in this case?

Accepted Answer

Excessive NK cell activity leads to tissue damage while attempting to control the virus.

Question 20

Which of the following is a correct sequence of events in the activation of the adaptive immune response to a viral infection?

Accepted Answer

APCs present viral antigens to T cells → Helper T cells activate B cells → B cells produce antibodies.

Host Resistance to Viral Infection: Mechanisms and Immune Responses

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