Block 9 Micro Viral Immunology

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    As a means of virulence, some viruses down-modulate class I major histocompatibility complex (MHC-I) cell surface expression of the cells they infect, thereby sharply diminishing CD8+ T lymphocyte-mediated cytoxicity efficiency. Yet, viral populations can still be kept in check despite the lack of CD8+ T lymphocyte-mediated cytotoxicity. Which of the following cells are the most likely to be responsible for killing infected cells that express very low levels of MHC-I?

    • NK cells
    • Macrophages
    • Dendritic cells
    • Neutrophils
    • B-lymphocytes
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Immunology Quizzes & Trivia
About This Quiz

Explore key concepts of viral immunology in 'Block 9 Micro viral immunology'. This quiz assesses understanding of antiviral defense mechanisms, including IFN-a activity, CD8+ T lymphocyte cytotoxicity, and innate host defenses. It's designed for learners aiming to deepen their knowledge in viral immunology.

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  • 2. 

    Which structure serves as the target for neutralizing antibodies when dealing with a naked, (+) ssRNA virus?

    • RNA

    • Capsid

    • Lipid bilayer

    • Envelope glycoprotein

    • RNA polymerase

    Correct Answer
    A. Capsid
    Explanation
    The correct answer is Capsid. The capsid is the protein coat that surrounds the RNA genome of a virus. In the case of a naked, (+) ssRNA virus, the capsid is the structure that serves as the target for neutralizing antibodies. These antibodies bind to the capsid and prevent the virus from infecting host cells. The RNA, lipid bilayer, envelope glycoprotein, and RNA polymerase are not the primary targets for neutralizing antibodies in this specific scenario.

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  • 3. 

    What are the most important hallmarks of antiviral defense?

    • Cell-mediated (CD8+) cytotoxicity and IFN-a secretion

    • Alternate activation of the complement pathway and IgM secretion

    • Cell-mediated (CD8+) cytotoxicity and IL-4 secretion

    • Classical activation of the complement pathway and IL-17 secretion

    Correct Answer
    A. Cell-mediated (CD8+) cytotoxicity and IFN-a secretion
    Explanation
    Cell-mediated (CD8+) cytotoxicity and IFN-a secretion are the most important hallmarks of antiviral defense. Cell-mediated cytotoxicity refers to the ability of CD8+ T cells to recognize and kill virus-infected cells, thereby preventing viral replication and spread. IFN-a secretion, on the other hand, is a type of interferon that plays a crucial role in activating immune cells and enhancing their antiviral activity. This combination of cell-mediated cytotoxicity and IFN-a secretion helps to eliminate virus-infected cells and control the spread of the virus within the body.

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  • 4. 

    Host defense against viral infections relies on a strong TH1 response. Which cytokines characterize the TH1 response?

    • IFN-y and IL-12

    • IL-4 and IFN-y

    • IL-4 and IL-12

    • IL-10 and IFN-y

    • IL-4 and TNF-a

    Correct Answer
    A. IFN-y and IL-12
    Explanation
    The TH1 response is characterized by the production of IFN-y and IL-12. These cytokines play a crucial role in activating macrophages and cytotoxic T cells, which are important for eliminating viral infections. IFN-y stimulates the production of antiviral proteins and enhances the killing ability of cytotoxic T cells, while IL-12 promotes the differentiation of TH1 cells and enhances their ability to produce IFN-y. Therefore, the presence of IFN-y and IL-12 is indicative of a strong TH1 response in host defense against viral infections.

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  • 5. 

    The expression of the genes encoding Pkr, 2’,5’-oligo(A) synthetase and RNase L is primarily under the control of which signalling pathway?

    • Erk1/Erk2 MAPK

    • NF-kB

    • SAPK/JNK

    • Jak/STAT

    • PI3K/Akt

    Correct Answer
    A. Jak/STAT
    Explanation
    The expression of the genes encoding Pkr, 2',5'-oligo(A) synthetase, and RNase L is primarily under the control of the Jak/STAT signaling pathway.

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  • 6. 

    Why is class I-restricted major histocompatibility complex (MHC-I) antigen presentation so important for viral clearance?

    • Because MHC-I restricted antigen presentation is the first step in the production of neutralizing antibodies

    • Because MHC-I restricted antigen presentation is the first step in the activation of both T helper 1 and T helper 2 responses

    • Because MHC-I restricted antigen presentation is the main pathway through which virus-infected cells are killed

    • Because MHC-I restricted antigen presentation is the main pathway of antibody-dependent cell-mediated cytotoxicity (ADCC)

    • Because MHC-I restricted antigen presentation is required for B-cell clonal expansion

    Correct Answer
    A. Because MHC-I restricted antigen presentation is the main pathway through which virus-infected cells are killed
    Explanation
    MHC-I restricted antigen presentation is important for viral clearance because it is the main pathway through which virus-infected cells are killed. MHC-I molecules present viral antigens on the surface of infected cells, allowing cytotoxic T cells to recognize and destroy these cells. This is a crucial mechanism in the immune response against viral infections, as it helps to eliminate the source of the virus and prevent its spread to other cells.

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  • 7. 

    Which structure serves as the target for neutralizing antibodies when dealing with an enveloped, (-) ssRNA virus?

    • RNA

    • Capsid

    • Lipid bilayer

    • Envelope glycoprotein

    • RNA polymerase

    Correct Answer
    A. Envelope glycoprotein
    Explanation
    Neutralizing antibodies target the envelope glycoprotein of enveloped, (-) ssRNA viruses. The envelope glycoprotein is located on the surface of the virus and plays a crucial role in viral entry and infection. By targeting this protein, neutralizing antibodies can prevent the virus from attaching to host cells and entering them, thereby neutralizing the virus and preventing infection.

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  • 8. 

    How does IFN-a exert its antiviral activity?

    • Virus neutralization

    • Activation of classical complement cascade

    • Extracellular degradation of virions

    • Pkr protein synthesis

    • Inhibition Jak/STAT signalling

    Correct Answer
    A. Pkr protein synthesis
    Explanation
    IFN-a exerts its antiviral activity through the synthesis of Pkr protein. Pkr protein is an enzyme that is activated in response to viral infection. Once activated, Pkr protein inhibits protein synthesis in infected cells, preventing the virus from replicating and spreading. This helps to control the viral infection and limit its impact on the host.

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  • 9. 

    Type I interferons (IFN-a/IFN-B) are the most important cytokines responsible for the induction of an antiviral state in virus-infected cells, as well as their neighbouring cells. Which of the following cascade of events is triggered by IFN-a?

    • IFN-a increases inactive RNA-activated protein kinase (Pkr) expression which, upon activation by double-stranded RNA, inactivates the translation activator eIF2 thereby terminating mRNA translation and promoting apoptosis and autophagy.

    • IFN-a decreases immunoproteasome expression, thereby leading to decreased protein degradation, decreased levels of major histocompatibility complex class I (MHC-I) cell surface expression, and increased natural killer cell cytotoxicity.

    • IFN-a increases the expressions of both 2’,5’-oligo(A) synthetase and RNase L, after which double-stranded RNA activates 2’,5’-oligo(A) synthetase to hydrolyze 2’,5’-adenylic acid thereby activating RNase L which degrades double-stranded RNA and sends the cell into apoptosis.

    • IFN-a increases inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate-oxidase (NADPH-oxidase) expressions, thereby decreasing the levels of free radicals in the cell and promoting apoptosis and autophagy.

    Correct Answer
    A. IFN-a increases inactive RNA-activated protein kinase (Pkr) expression which, upon activation by double-stranded RNA, inactivates the translation activator eIF2 thereby terminating mRNA translation and promoting apoptosis and autophagy.
    Explanation
    IFN-a increases the expression of inactive RNA-activated protein kinase (Pkr) which, when activated by double-stranded RNA, inactivates the translation activator eIF2. This leads to the termination of mRNA translation and promotes apoptosis and autophagy.

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  • 10. 

    The hallmarks of antiviral immunity are type I IFN-dependent defense mechanisms (IFN-and IFN-), NK cell cytotoxicity, CD8+ T lymphocyte cytotoxicity, as well as antibody production for virus neutralization, opsonization and ADCC. The CD8+ T lymphocyte cytotoxicity response is orchestrated by which of these cell types?

    • Natural killer cells (NK cells)

    • Macrophages

    • CD4+ T helper 2 lymphocytes

    • B-lymphocytes

    Correct Answer
    A. Macrophages
    Explanation
    Macrophages play a crucial role in orchestrating the CD8+ T lymphocyte cytotoxicity response. They act as antigen-presenting cells, presenting viral antigens to CD8+ T cells to initiate their activation and cytotoxicity. Macrophages also produce cytokines and chemokines that attract and activate CD8+ T cells. Therefore, they are essential for coordinating the immune response against viral infections.

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  • 11. 

    Which of these is not an innate host defense mechanism?

    • Virus neutralization

    • Apoptosis

    • IFN-a secretion

    • Alternative activation of the complement pathway

    • Autophagy

    Correct Answer
    A. Virus neutralization
    Explanation
    Virus neutralization is not an innate host defense mechanism because it is primarily a function of the adaptive immune system. Innate host defense mechanisms are the body's first line of defense against pathogens and are present from birth. These mechanisms include apoptosis, IFN-a secretion, alternative activation of the complement pathway, and autophagy. Virus neutralization, on the other hand, involves the production of specific antibodies by B cells in response to a viral infection, which is a characteristic of the adaptive immune response.

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  • 12. 

    A patient recently diagnosed with hepatitis B undergoes interferon-(IFN-) treatment for his viral infection (Hepatitis B virus). Which of the following mechanisms is the basis of this therapeutic approach?

    • IFN-a decreases mRNA transcription consequent to Pkr up-regulation in virally-infected cells.

    • IFN-a decreases mRNA transcription consequent to eIF2- dephosphorylation in virally-infected cells.

    • IFN-a decreases mRNA transcription consequent to RNase L down-regulation in virally-infected cells.

    • IFN-a decreases mRNA translation consequent to Pkr up-regulation in virally-infected cells.

    Correct Answer
    A. IFN-a decreases mRNA translation consequent to Pkr up-regulation in virally-infected cells.
    Explanation
    Interferon-α (IFN-α) treatment for hepatitis B works by decreasing mRNA translation in virally-infected cells through the up-regulation of Pkr. This means that IFN-α increases the activity of Pkr, which in turn inhibits the translation of viral mRNA, ultimately reducing viral protein synthesis. By decreasing viral protein production, IFN-α helps to suppress the replication and spread of the hepatitis B virus in the patient's body.

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  • 13. 

    CD8+ T lymphocytes usually contain viral infections by destroying infected cells in an MHC-I-restricted fashion. However, CD8+ T lymphocytes are also capable of purging virally-infected cells in a non-cytolytic way. Which cytokine is responsible for this?

    • IFN-a

    • TNF-a

    • IL-1

    • IL-6

    • IFN-y

    Correct Answer
    A. IFN-y
    Explanation
    IFN-y, also known as interferon-gamma, is responsible for the non-cytolytic purging of virally-infected cells by CD8+ T lymphocytes. This cytokine activates macrophages and enhances their ability to eliminate intracellular pathogens, including viruses. It also promotes the production of antibodies and increases the expression of MHC molecules, aiding in the recognition and clearance of infected cells. Therefore, IFN-y plays a crucial role in the immune response against viral infections by CD8+ T lymphocytes.

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  • 14. 

    Which is the most likely receptor that will initiate the cascade leading to type I IFN expression in virus-infected cells?

    • Interferon receptor

    • Toll-like receptor

    • Jak receptor

    • Tumor necrosis alpha receptor

    • T cell receptor

    Correct Answer
    A. Toll-like receptor
    Explanation
    Toll-like receptors are a class of proteins that play a key role in the innate immune response. They recognize specific patterns on pathogens, including viruses, and initiate a signaling cascade that leads to the expression of type I interferons (IFNs). These IFNs are important in the antiviral response, activating various immune cells and promoting the production of antiviral proteins. Therefore, the most likely receptor that will initiate the cascade leading to type I IFN expression in virus-infected cells is the Toll-like receptor.

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  • 15. 

    Which is the most likely receptor that will initiate the cascade leading to type I IFN expression in virus-infected cells?

    • Interferon receptor

    • RIG-1

    • Jak receptor

    • Tumor necrosis alpha receptor

    • T cell receptor

    Correct Answer
    A. RIG-1
    Explanation
    RIG-1 is the most likely receptor that will initiate the cascade leading to type I IFN expression in virus-infected cells. RIG-1 is a pattern recognition receptor (PRR) that recognizes viral RNA and activates the innate immune response. Upon binding to viral RNA, RIG-1 triggers a signaling cascade that leads to the production of type I interferons, which are key molecules in antiviral defense. Therefore, RIG-1 is the most likely receptor involved in initiating the cascade leading to type I IFN expression in virus-infected cells.

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  • Current Version
  • Feb 19, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jun 07, 2012
    Quiz Created by
    Chachelly

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