Immunology Year 1: Intracellular Infections
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Questions and Answers

The immune system's goal for extracellular pathogens is to kill the pathogen.

True

Antibodies are primarily involved in the immune response against intracellular pathogens.

False

Neutrophils and macrophages are important for responding to extracellular bacteria.

True

Cytotoxic T cells are essential for eliminating infected cells due to intracellular pathogens.

<p>True</p> Signup and view all the answers

Th2 cells and IgE antibodies are primarily involved in the immune response to helminths.

<p>True</p> Signup and view all the answers

Viruses can evade the immune response by down-regulating MHC class I.

<p>True</p> Signup and view all the answers

Antigenic drift involves major changes in viral antigens.

<p>False</p> Signup and view all the answers

The Epstein Barr Virus has a protein that inhibits antigen processing.

<p>True</p> Signup and view all the answers

Influenza virus evasion is primarily due to antigenic drift and antigenic shift.

<p>True</p> Signup and view all the answers

Down-regulated MHC class I makes cells immune to NK cells.

<p>False</p> Signup and view all the answers

Point mutations lead to antigenic drift in viruses.

<p>True</p> Signup and view all the answers

Antigenic shift does not occur in influenza viruses.

<p>False</p> Signup and view all the answers

Viral genetic variation can prevent recognition by the immune system.

<p>True</p> Signup and view all the answers

HSV aids in peptide generation for immune response.

<p>False</p> Signup and view all the answers

Cells can become targets for NK cells after down-regulating MHC class I.

<p>True</p> Signup and view all the answers

Innate immune cells have specific antigen receptors.

<p>False</p> Signup and view all the answers

NK cells can detect 'altered self' cells.

<p>True</p> Signup and view all the answers

The primary function of NK cells is to directly kill pathogens.

<p>False</p> Signup and view all the answers

NK cells possess both inhibitory and activatory receptors.

<p>True</p> Signup and view all the answers

Normal, uninfected cells trigger NK cell activation.

<p>False</p> Signup and view all the answers

Infected cells down-regulate MHC class I to escape NK cell detection.

<p>False</p> Signup and view all the answers

NK cells kill infected cells in a similar manner to cytotoxic T cells.

<p>True</p> Signup and view all the answers

NK cells require a positive signal from either inhibitory or activatory receptors to function.

<p>False</p> Signup and view all the answers

Perforin forms pores in the membrane of infected cells.

<p>True</p> Signup and view all the answers

Cytotoxic T lymphocytes (CTL) kill pathogens directly.

<p>False</p> Signup and view all the answers

Granzyme is involved in activating apoptosis in infected cells.

<p>True</p> Signup and view all the answers

Cytotoxic T cells recognize viral antigens presented on MHC class II molecules.

<p>False</p> Signup and view all the answers

The cytokine IFN-γ drives Th1 responses.

<p>True</p> Signup and view all the answers

Antibody effector mechanisms are significant for anti-viral immunity.

<p>False</p> Signup and view all the answers

A virally-infected cell displays viral antigens on MHC class II molecules.

<p>False</p> Signup and view all the answers

Activated cytotoxic T cells release vesicles containing toxic enzymes.

<p>True</p> Signup and view all the answers

Genetic recombination between different viruses can create a completely new virus with no historical immunity.

<p>True</p> Signup and view all the answers

Th1 cells are primarily important for fighting viral infections.

<p>False</p> Signup and view all the answers

IFN-γ enhances the activation of macrophages by upregulating costimulatory molecules.

<p>True</p> Signup and view all the answers

Granulomas can form as a result of Th1 induced macrophage activation.

<p>True</p> Signup and view all the answers

The center of a granuloma may become hyperoxic and undergo necrosis.

<p>False</p> Signup and view all the answers

The MTb bacteria can persist within granulomas for years while the host maintains good health.

<p>True</p> Signup and view all the answers

Steroid treatment can reactivate dormant MTb infections.

<p>True</p> Signup and view all the answers

Ongoing Th1 response is not necessary for lifelong control of infections.

<p>False</p> Signup and view all the answers

Macrophages are activated by Th1 cells to kill Mycobacterium tuberculosis (MTb).

<p>True</p> Signup and view all the answers

IL-12 is a factor that promotes the activation of Th2 cells.

<p>False</p> Signup and view all the answers

Interferons play a significant role in the anti-viral response.

<p>True</p> Signup and view all the answers

Natural Killer cells are exclusively responsible for the adaptive immune response.

<p>False</p> Signup and view all the answers

Granulomas are involved in the response to intracellular bacteria.

<p>True</p> Signup and view all the answers

The immune system recognizes both viruses and extracellular bacteria with the same response.

<p>False</p> Signup and view all the answers

Cytotoxic T cells are important for dealing with intracellular infections.

<p>True</p> Signup and view all the answers

The innate immune response comes days to weeks after infection.

<p>False</p> Signup and view all the answers

Pathogenic fungi are only recognized by the adaptive immune system.

<p>False</p> Signup and view all the answers

The use of influenza helps describe a typical immune response to viral infection.

<p>True</p> Signup and view all the answers

Adaptive immunity is not involved in the response to extracellular fungi.

<p>False</p> Signup and view all the answers

Viruses can escape immune detection and may contribute to disease pathology.

<p>True</p> Signup and view all the answers

Type I interferons (IFNs) induce an anti-viral immune state that potentially shuts down nearby infected cells.

<p>True</p> Signup and view all the answers

Natural Killer (NK) cells solely rely on MHC class I molecules for activation.

<p>False</p> Signup and view all the answers

Viral RNA is recognized by TLR2 and TLR6 receptors.

<p>False</p> Signup and view all the answers

The innate immune response to viruses is characterized by the activation of NK cells and macrophages.

<p>True</p> Signup and view all the answers

Cytotoxic T cells directly kill infected cells by releasing antibodies.

<p>False</p> Signup and view all the answers

Activation of dendritic cells and macrophages is a significant effect of Type I IFNs on the immune response.

<p>True</p> Signup and view all the answers

Cells that down-regulate MHC class I become targets for NK cells.

<p>True</p> Signup and view all the answers

Granzyme is involved in the metabolic activation of macrophages by T cells.

<p>False</p> Signup and view all the answers

Inhibitory receptors on NK cells bind to MHC class II molecules.

<p>False</p> Signup and view all the answers

NK cells can be activated when there is no positive signal from the inhibitory receptor.

<p>True</p> Signup and view all the answers

Viruses have developed strategies solely to enhance their reproduction, disregarding immune evasion.

<p>False</p> Signup and view all the answers

Uninfected cells do not provide any inhibitory signaling to NK cells.

<p>False</p> Signup and view all the answers

Type I interferons play a critical role in the innate immune response to viruses.

<p>True</p> Signup and view all the answers

Virally-infected cells down-regulate MHC class I to avoid detection by cytotoxic T cells (CTLs).

<p>True</p> Signup and view all the answers

The goal of viruses is to thrive in a hostile environment rather than to survive.

<p>False</p> Signup and view all the answers

NK cells have antigen-specific receptors similar to those of cytotoxic T cells.

<p>False</p> Signup and view all the answers

Cytokines, including pro-inflammatory cytokines, are not involved in the innate immune response to viruses.

<p>False</p> Signup and view all the answers

Activation of NK cells involves recognizing the presence of tumor cells.

<p>True</p> Signup and view all the answers

The immune system is a versatile opponent against viruses aimed at survival.

<p>True</p> Signup and view all the answers

The presence of activatory receptors on NK cells prevents them from killing infected cells.

<p>False</p> Signup and view all the answers

NK cells kill infected cells using a mechanism similar to cytotoxic T lymphocytes (CTLs).

<p>True</p> Signup and view all the answers

Cytotoxic T Lymphocytes (CTL) are programmed to kill cells that display viral antigens on MHC class I molecules.

<p>True</p> Signup and view all the answers

Perforin and granzymes are involved in the killing of extracellular pathogens.

<p>False</p> Signup and view all the answers

The cytokine IFN-γ plays a significant role in driving Th2 responses.

<p>False</p> Signup and view all the answers

Activated cytotoxic T cells release perforin to promote apoptosis in infected cells.

<p>True</p> Signup and view all the answers

Virally-infected cells do not express any antigens.

<p>False</p> Signup and view all the answers

Cytotoxic T cells primarily attack pathogens directly rather than the cells infected by them.

<p>False</p> Signup and view all the answers

Granzymes activate apoptosis regardless of the presence of perforin.

<p>False</p> Signup and view all the answers

Cytotoxic T cells play an insignificant role in anti-viral immunity.

<p>False</p> Signup and view all the answers

Eosinophils and mast cells are important for the immune response to helminths.

<p>True</p> Signup and view all the answers

The primary goal of the immune system when dealing with intracellular pathogens is to kill the pathogens directly.

<p>False</p> Signup and view all the answers

Th17 cells are primarily involved in the immune response against extracellular bacteria.

<p>False</p> Signup and view all the answers

Interferon response is crucial for managing infections caused by viruses.

<p>True</p> Signup and view all the answers

Intracellular bacteria activate Th2 cells to promote the immune response.

<p>False</p> Signup and view all the answers

Antigenic drift refers to subtle changes in surface antigens of viruses due to major mutations.

<p>False</p> Signup and view all the answers

Influenza viruses evade the immune response through antigenic shift and antigenic drift.

<p>True</p> Signup and view all the answers

Down-regulating MHC class I protects cells from being targeted by NK cells.

<p>False</p> Signup and view all the answers

Major changes in viral antigens caused by genetic recombination are a characteristic of antigenic drift.

<p>False</p> Signup and view all the answers

Viral genetic variation can lead to mutations that prevent recognition by immune cells.

<p>True</p> Signup and view all the answers

Interfering with antigen processing does not impact the detection of viruses by the immune system.

<p>False</p> Signup and view all the answers

Cells that successfully down-regulate MHC class I are likely to experience increased immune recognition.

<p>False</p> Signup and view all the answers

Antigenic shift occurs rarely compared to antigenic drift in influenza viruses.

<p>True</p> Signup and view all the answers

HSV aids in efficient peptide generation for the immune response.

<p>False</p> Signup and view all the answers

Type I interferons (IFNs) are produced by uninfected cells.

<p>False</p> Signup and view all the answers

The activation of cytotoxic T cells is solely dependent on the presence of TLR receptors.

<p>False</p> Signup and view all the answers

Natural Killer (NK) cells have no role in recognizing 'altered self' cells.

<p>False</p> Signup and view all the answers

MHC class I upregulation is a direct effect of type I interferons on immune cells.

<p>True</p> Signup and view all the answers

Intracellular infections primarily trigger an adaptive immune response without the involvement of innate immunity.

<p>False</p> Signup and view all the answers

RIG-I receptors are involved in recognizing viral capsid proteins.

<p>False</p> Signup and view all the answers

Cytotoxic T lymphocytes (CTL) are primarily activated by type I interferons.

<p>False</p> Signup and view all the answers

Type I IFNs can directly shut down infected cells to limit the spread of viruses.

<p>True</p> Signup and view all the answers

Virally-infected cells primarily produce IL-10 as their main cytokine.

<p>False</p> Signup and view all the answers

CTLs and NK cells are responsible for killing virally-infected cells.

<p>True</p> Signup and view all the answers

Antibodies have only one role, which is to neutralize viruses.

<p>False</p> Signup and view all the answers

Viruses can evade the host immune response by mutating their surface proteins.

<p>True</p> Signup and view all the answers

Th17 and Th1 cells are equally effective in eliminating virally-infected cells.

<p>False</p> Signup and view all the answers

Complement activation is not a function of antibodies against viruses.

<p>False</p> Signup and view all the answers

Down-regulation of MHC class I enhances the recognition of infected cells by NK cells.

<p>False</p> Signup and view all the answers

The innate immune response in humans occurs within hours of infection.

<p>True</p> Signup and view all the answers

Granzyme is responsible for forming pores in the membrane of infected cells.

<p>False</p> Signup and view all the answers

Cytotoxic T lymphocytes primarily kill pathogens directly rather than infected cells.

<p>False</p> Signup and view all the answers

IFN-γ is a cytokine that enhances Th2 responses.

<p>False</p> Signup and view all the answers

Virally-infected cells display viral antigens on MHC class I molecules to be recognized by cytotoxic T cells.

<p>True</p> Signup and view all the answers

Granulomas are primarily formed in response to viral infections.

<p>False</p> Signup and view all the answers

Activated cytotoxic T cells release perforin and granzymes to eliminate infected cells.

<p>True</p> Signup and view all the answers

The expression of MHC class I on a cell is irrelevant for the activation of cytotoxic T cells.

<p>False</p> Signup and view all the answers

Natural Killer cells are unable to recognize cells that down-regulate MHC class I molecules.

<p>False</p> Signup and view all the answers

The primary mechanisms of the innate immune response occur instantaneously, within minutes to hours.

<p>True</p> Signup and view all the answers

Adaptive immunity primarily targets extracellular pathogens without any involvement of innate immunity.

<p>False</p> Signup and view all the answers

Natural Killer cells are mainly responsible for targeting only extracellular bacteria during the immune response.

<p>False</p> Signup and view all the answers

Granulomas are formed as an adaptive immune response to control intracellular bacteria like Mycobacterium tuberculosis.

<p>True</p> Signup and view all the answers

Interferons are crucial mediators that enhance the body's antiviral response.

<p>True</p> Signup and view all the answers

Th1 cells are essential for the effective immune response against helminths.

<p>False</p> Signup and view all the answers

The process of antigenic drift in viruses results from gradual mutations that escape immune detection.

<p>True</p> Signup and view all the answers

NK cells kill uninfected cells by utilizing their activatory receptors.

<p>False</p> Signup and view all the answers

Cytokines play an essential role in the inflammatory response but are not involved in adaptive immunity.

<p>False</p> Signup and view all the answers

The immune system's recognition of both viruses and extracellular bacteria utilizes identical mechanisms.

<p>False</p> Signup and view all the answers

Virally-infected cells down-regulate MHC class I to avoid detection by cytotoxic T cells.

<p>True</p> Signup and view all the answers

NK cells can directly kill pathogens by themselves.

<p>False</p> Signup and view all the answers

Inhibitory receptors on NK cells increase their activation when they bind to MHC class I.

<p>False</p> Signup and view all the answers

Normal cells trigger a positive signal for NK cell activation.

<p>False</p> Signup and view all the answers

The mechanism of NK cell killing is fundamentally the same as that of cytotoxic T cells.

<p>True</p> Signup and view all the answers

NK cells have only inhibitory receptors and cannot activate without a positive signal.

<p>False</p> Signup and view all the answers

MHC class I down-regulation on infected cells leads to NK cell inactivation.

<p>False</p> Signup and view all the answers

Antigenic drift results in major alterations on the surface of the influenza virus due to events such as point mutations.

<p>False</p> Signup and view all the answers

Viruses can evade immune detection by up-regulating MHC class I expression.

<p>False</p> Signup and view all the answers

Antigenic shift occurs less frequently than antigenic drift and involves significant changes in the viral antigens.

<p>True</p> Signup and view all the answers

Epstein Barr Virus enhances antigen processing to help with immune evasion.

<p>False</p> Signup and view all the answers

The down-regulation of MHC class I makes cells more susceptible to attacks from NK cells.

<p>True</p> Signup and view all the answers

Cellular mechanisms that interfere with peptide generation can enhance a virus's ability to evade immune response.

<p>True</p> Signup and view all the answers

Small mutations in viral genes can result in loss of recognition by the immune system and contribute to ongoing infections.

<p>True</p> Signup and view all the answers

Major changes to viral antigens can occur due to genetic recombination of influenza viruses.

<p>True</p> Signup and view all the answers

The protein produced by Epstein Barr Virus enhances MHC class I expression on the cell surface.

<p>False</p> Signup and view all the answers

Cells that up-regulate MHC class I are less likely to be targeted by NK cells.

<p>True</p> Signup and view all the answers

Study Notes

Responses to Intracellular Infections

  • Presentation given by Dr. Patrick Walsh
  • Class Year 1
  • Module BMF
  • Date: November 2024

Immunology Lectures Outline

  • Barrier Immunity: Physical, mechanical, and chemical barriers
  • Innate Immunity: Cytokines, inflammation, complement, antigen presentation
  • Adaptive Immunity: Response to extracellular and intracellular infections, including cytotoxic and helper T cells, and antibodies

Lecture Learning Outcomes

  • Describe a typical immune response to viral infection (using influenza as an example) and the role of interferons, Natural Killer cells, and cytotoxic T cells in the anti-viral response
  • Define the adaptive immune response to viral infection and how viruses escape immune detection, leading to disease pathology
  • Using mycobacterium as an example, describe the innate and adaptive immune response to intracellular bacteria and granuloma development/maintenance

Extracellular vs. Intracellular

  • Extracellular: Bacteria, fungi, protozoa, helminths, interstitial spaces, blood, lymph, epithelial surfaces
  • Intracellular: Viruses, bacteria, fungi, protozoa, cytoplasmic, vesicular

How Does the Immune System Recognize Viruses?

  • Viral pattern recognition receptors, including:
    • Viral capsid proteins: TLR2/6 & TLR4
    • Viral RNA (RNA virus): TLR3
    • Cytoplasmic RNA receptors: RIG-I

Overview of Immune Response to Intracellular Infections

  • Innate immunity: NK cells, Type I IFNs
  • Adaptive immunity: Virus-specific CTLs, antibodies
  • Timeline (graph shown) indicates the relative timing of responses

Innate Immune Response to Viruses

  • Recognition by infected cells
  • Production of type I interferons (IFNs)
  • Induction of an anti-viral state in infected and nearby cells
  • Increase of antigen presentation in all cells
  • Activation of innate immune cells (NK cells, macrophages, dendritic cells)
  • Induction of adaptive immunity

Effects of Type I IFNs on Immune Cells

  • Up-regulation of MHC class I
  • Activation of dendritic cells and macrophages
  • Activation of cytotoxic T cells (directly kill infected cells)
  • Activation of NK cells (directly kill infected cells)

NK Cells in Anti-viral Innate Immune Response

  • Innate immune cells
  • No specific antigen receptor
  • Detect "altered self" cells
  • Kill virally-infected and tumor cells
  • Do not kill pathogens, though they kill infected cells Mechanism: -Inhibitory receptor bound to MHC class I
  • Activatory receptor bound to virally-infected cells
  • Cytotoxic action (pore formation, enzyme release)

NK Cells Mechanism of Action

  • Kill virally infected cells by the same way as CTLs
    • Perforin
    • Granzyme
    • Cell death (apoptosis)
    • Release of cytokine IFN-y (drives Th1 responses and CTL activity)

Antibody effector mechanisms against viruses

  • Neutralization (prevents adherence)
  • Opsonization ( antibody blocks microbe binding)
  • Complement activation (insignificant for anti-viral immunity)

Cytotoxic T Lymphocytes (CTL) Activation

  • Virally infected cells display viral antigens on MHC class I molecules
  • CTLs recognize the displayed antigens and bind
  • CTLs release cytotoxic granules to execute infected cells via apoptosis

Cytotoxic T Lymphocyte (CTL) Killing

  • Recognition of virally infected cells via MHC Class I molecules displayed on their surfaces
  • Activation of the CTLs
  • Vesicle release containing perforin and granzymes to kill the infected cells
  • Killing of infected cells due to the activation of apoptosis

Follow the Influenza Virus

  • Main cytokine produced by virally-infected cells: IFN-a/b
  • Immune cells responsible for killing virally-infected cells: CTLs and NK cells
  • Role of antibodies against viruses: Insignificant for killing viruses (neutralization/opsonization, etc.)

How can Viruses Learn to Evade the Host Immune Response?

  • Viruses evolve evasion techniques

Mechanisms of How Viruses Evade the Immune Response

  • Viral genetic variation: mutations prevent recognition by MHC class 1
  • Downregulation of MHC class I
  • Interference with antigen processing (Epstein Barr Virus and HSV)

Other Immune Evasion by Influenza

  • Antigenic shift: major changes in viral antigens caused by genetic recombination between different viruses
  • Completely new virus created. Nobody has previous or historical immunity
  • Doesn't happen frequently

Th1 Cells and Mycobacterial Infections

  • Th1 cells are important in fighting mycobacterial infections
  • Key functions:
    • Potent macrophage activation
    • Increased MHC class I and II expression for antigen presentation
    • Induction of nitric oxide synthase and ROS production

Th1 Cells and the Killing of MTB

  • IFN-γ activates the macrophages to kill mycobacteria (MTB) by upregulating various molecules (e.g., CD80/86, CD40), increasing MHC expression, and activating nitric oxide synthase
  • Enhanced microbial activity and activation of Th1 and cytotoxic T cells

Granuloma Formation

  • Th1 induced macrophage maturation and granuloma formation
  • Infection sealed off by immune cells
  • Hypoxic center and necrosis
  • MTB persistence for prolonged periods
  • Reactivation by treatment (e.g., steroids, or malnutrition)

Immune Responses - Summary of Today's Lectures

  • Extracellular pathogens: Neutrophils, macrophages, Th17, antibodies, eosinophils, and mast cells (for helminths)
  • Intracellular pathogens: IFN response, NK cells, CTLs, antibody neutralization (viruses), and Th1 and IFN-γ for intracellular bacteria

SGT - A Healthy Immune Response

  • XX November Immunology tutorial, divided into small groups
  • Students must pre-read the reference
  • Feedback on the lecture content or delivery can be given via www.menti.com

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Description

This quiz focuses on the immune responses to intracellular infections as outlined in Dr. Patrick Walsh's lecture. It covers key concepts like barrier immunity, innate and adaptive immunity, and the role of various immune cells in response to viral infections. Prepare to test your knowledge on critical concepts that underlie the immune system's function against pathogens.

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