Immune Response Pathways
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Questions and Answers

What is the significance of the name 'natural killer' in the context of immune cells?

  • They do not need prior activation to function. (correct)
  • They are only found in the classical pathway.
  • They are part of the adaptive immune system.
  • They require prior activation to function.

    • What is the difference between the alternative pathway and the classical pathway in terms of phylogenetic age?

  • The age of the pathways is not a relevant factor.
  • The classical pathway is phylogenetically older than the alternative pathway. (correct)
  • The alternative pathway is equally old as the classical pathway.
  • The alternative pathway is phylogenetically younger than the classical pathway.

    • What is the consequence of the alternative pathway's inefficiency in tissues?

  • Only a single component is required.
  • Low concentrations of components are required.
  • No components are required.
  • High concentrations of components are required. (correct)

    • What is the purpose of the three mechanisms that control the complement pathway?

    <p>To prevent the production of self-damaging mediators of inflammation.</p> Signup and view all the answers

    What type of agents can activate natural killer cells further?

    <p>Non-specific agents, such as mitogens, IFN-γ and IL-12.</p> Signup and view all the answers

    What is the significance of natural killer cells having the relevant recognition molecules on their surface?

    <p>They can function without prior activation.</p> Signup and view all the answers

    What is the mechanism by which antibody-coated target cells are destroyed?

    <p>Antibody-dependent cell-mediated cytotoxicity</p> Signup and view all the answers

    What is the role of FcRIII in the context of Natural Killer cells?

    <p>Antibody-dependent cell-mediated cytotoxicity</p> Signup and view all the answers

    What is the purpose of granzymes and perforin in Natural Killer cells?

    <p>Cytolysis of target cells</p> Signup and view all the answers

    What is the role of the inhibitory receptor KIR in Natural Killer cells?

    <p>Inhibition of cytotoxicity</p> Signup and view all the answers

    What is the role of IFN-γ and TNF-α in the context of Natural Killer cells?

    <p>Cytokine production and immune activation</p> Signup and view all the answers

    What is the role of MHC class I in the context of Natural Killer cells?

    <p>Inhibition of Natural Killer cell activity</p> Signup and view all the answers

    What is the primary function of Natural Killer cells?

    <p>To recognize and eliminate virally infected cells or tumor cells</p> Signup and view all the answers

    Where are Natural Killer cells predominantly found?

    <p>In the blood, liver, and secondary lymphoid organs</p> Signup and view all the answers

    What is the mechanism by which Natural Killer cells kill target cells?

    <p>Through the release of perforin and granzymes</p> Signup and view all the answers

    What is the relationship between Natural Killer cells and cytotoxic T cells?

    <p>Natural Killer cells and cytotoxic T cells have distinct functions in the immune response</p> Signup and view all the answers

    What is the role of Natural Killer cells in the early immune response to viral infections?

    <p>To recognize and eliminate virally infected cells</p> Signup and view all the answers

    What is the morphology of Natural Killer cells?

    <p>They are large, granular lymphocytes</p> Signup and view all the answers

    What is the role of Natural Killer cells in tumor surveillance?

    <p>To recognize and eliminate tumor cells</p> Signup and view all the answers

    What is the relationship between Natural Killer cells and type-I interferons?

    <p>Natural Killer cells are activated by type-I interferons</p> Signup and view all the answers

    What is the main difference between natural killer cells and adaptive immune cells?

    <p>Their requirement for prior activation before responding to target cells</p> Signup and view all the answers

    What is the consequence of the alternative pathway's inefficiency in tissues?

    <p>The production of excessive amounts of inflammatory mediators</p> Signup and view all the answers

    What is the purpose of the mechanisms that control the complement pathway?

    <p>To prevent the production of self-damaging mediators of inflammation</p> Signup and view all the answers

    What is the role of non-specific agents in natural killer cell activation?

    <p>To further activate natural killer cells</p> Signup and view all the answers

    What is the significance of natural killer cells having recognition molecules on their surface?

    <p>They can respond to target cells immediately without prior activation</p> Signup and view all the answers

    What is the consequence of the production of self-damaging mediators of inflammation?

    <p>Tissue damage and inflammation</p> Signup and view all the answers

    What is the function of C5a in the complement pathway?

    <p>To attract neutrophils to the site of complement activation and increase vascular permeability</p> Signup and view all the answers

    Which of the following cells can kill target cells without antibody or antigenic stimulation?

    <p>Natural killer cells</p> Signup and view all the answers

    What is the role of C3b in the complement pathway?

    <p>To bind to the initiating complex and promote biological properties of complement</p> Signup and view all the answers

    What is the morphology of Natural killer cells?

    <p>Large granular lymphocytes</p> Signup and view all the answers

    What is the primary function of the C4b2b3b complex in the complement pathway?

    <p>To initiate the final lytic pathway</p> Signup and view all the answers

    What is the role of Natural killer cells in the early immune response to viral infections?

    <p>To kill target cells in the absence of antibody or antigenic stimulation</p> Signup and view all the answers

    What is the relationship between Natural killer cells and cytotoxic T cells?

    <p>Both Natural killer cells and cytotoxic T cells are involved in late immune responses</p> Signup and view all the answers

    Where are Natural killer cells predominantly found?

    <p>Spleen and mucosal associated lymphoid tissue (MALT)</p> Signup and view all the answers

    What is the primary mechanism by which antibody-coated target cells are destroyed through Antibody-dependent Cell-mediated Cytotoxicity?

    <p>By the interaction between FcRIII and the antibody</p> Signup and view all the answers

    What is the role of FcRIII in the context of Antibody-dependent Cell-mediated Cytotoxicity?

    <p>It binds to the antibody and triggers the destruction of the target cell</p> Signup and view all the answers

    What is the consequence of the interaction between the inhibitory receptor KIR and MHC class I on the target cell?

    <p>It prevents the destruction of the target cell through Natural Killer cells</p> Signup and view all the answers

    What is the role of Natural Killer cells in the context of Antibody-dependent Cell-mediated Cytotoxicity?

    <p>They interact with FcRIII to trigger the destruction of target cells</p> Signup and view all the answers

    What is the result of the interaction between the antibody and FcRIII on the surface of Natural Killer cells?

    <p>The destruction of the target cell through Antibody-dependent Cell-mediated Cytotoxicity</p> Signup and view all the answers

    What is the relationship between Antibody-dependent Cell-mediated Cytotoxicity and the destruction of target cells?

    <p>Antibody-dependent Cell-mediated Cytotoxicity is a mechanism by which antibody-coated target cells are destroyed</p> Signup and view all the answers

    Study Notes

    Complement Pathway

    • The alternative pathway is phylogenetically older than the classical pathway.
    • The alternative pathway is relatively inefficient in tissues and requires high concentrations of components.
    • The central reaction in the alternative pathway is the formation of two fragments, C3a and C3b, which have anaphylotoxic, chemotactic, and binding properties.

    Control of Complement Pathway

    • The complement pathway is controlled by three mechanisms to prevent harmful effects of inflammation.
    • C5a and C3a are anaphylotoxins that cause histamine release from mast cells, increasing vascular permeability.
    • C5a is also chemotactic, attracting neutrophils to the site of complement activation.

    Natural Killer Cells

    • Natural killer cells resemble large granular lymphocytes and are found in blood, liver, and secondary lymphoid organs.
    • NK cells can kill target cells without prior activation, antibody, or antigenic stimulation.
    • NK cells can recognize and kill target cells directly through secretion of granzymes or perforin, or indirectly through FcRIII and ADCC.
    • NK cells also secrete IFN-γ and TNF-α.
    • NK cells are activated by non-specific agents, such as mitogens, IFN-γ, and IL-12.
    • C5a, along with C3a, can activate NK cells further.

    Early Immune Response to Viral Infection

    • Early immune response to viral infection involves production of type-I interferons and IL-12 by innate immune cells.
    • NK cells play a role in the early immune response to viral infection, producing type-I interferons and IL-12.
    • Late immune response involves T cell-mediated killing by antigen-specific cells, including cytotoxic T cells (CTL).

    Complement Pathway

    • The alternative pathway is phylogenetically older than the classical pathway.
    • The alternative pathway is relatively inefficient in tissues and requires high concentrations of components.
    • The central reaction in the alternative pathway is the formation of two fragments, C3a and C3b, which possess anaphylotoxic and chemotactic activity and promote biological properties of complement.

    Complement Pathway Control

    • The complement pathway is controlled by three mechanisms (see Box 1.5).
    • These mechanisms ensure that the potentially harmful mediators of inflammation are regulated.

    Anaphylatoxins

    • C5a and C3a are anaphylatoxins that cause histamine release from mast cells, resulting in increased vascular permeability.
    • C5a is also chemotactic, attracting neutrophils to the site of complement activation.

    Natural Killer Cells

    • Natural killer cells look like large granular lymphocytes and are found in blood, liver, and secondary lymphoid organs, particularly the spleen and mucosal-associated lymphoid tissue (MALT).
    • NK cells can kill target cells, even in the absence of antibody or antigenic stimulation.
    • NK cells can kill target cells through direct secretion of granzymes or perforin, by FcRIII and ADCC, or by secretion of IFN-γ and TNF-α.
    • NK cells are regulated by the interaction between the inhibitory receptor (KIR) and MHC class I on the target cell.

    Early Immune Response to Virus Infection

    • Early immune response to virus infection involves the production of type-I interferons and IL-12 by innate immune cells.
    • NK cells are involved in the early immune response to virus infection, producing type-I interferons and IL-12.
    • Late immune response involves T cell-mediated killing by antigen-specific cells (cytotoxic T cells).

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    Description

    This quiz covers the natural killer cells and the alternative pathway of the immune system, comparing it to the classical pathway. It also discusses the production of self-damaging mediators.

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