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Theme 5a: Tolerance, Hypersensitivity, and Mucosal Immunity Part 1
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Theme 5a: Tolerance, Hypersensitivity, and Mucosal Immunity Part 1

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Questions and Answers

Which of the following mechanisms of peripheral tolerance occurs when self-antigens are not present in sufficient quantities to reach the threshold of activation for TCR?

  • Deletion
  • Ignorance (correct)
  • Suppression
  • Anergy

    • What is the term for the lack of TCR activation due to the lack of co-stimulation by APCs?

  • Tolerance
  • Hypersensitivity
  • Ignorance
  • Anergy (correct)

    • Which of the following is an example of an immunologically privileged site where self-antigens remain sequestered?

  • Thymus
  • Lymph node
  • Anterior chamber of the eye (correct)
  • Spleen

    • What is the purpose of central tolerance in the thymus?

    <p>To eliminate self-reactive T cells</p> Signup and view all the answers

    Which of the following mechanisms of peripheral tolerance involves the action of negative co-stimulatory pathways?

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

    What is the term for the process by which T cells are not activated due to the lack of self-antigens during early +/- selection in the thymus?

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

    What is the primary reason why the body maintains a state of immunological tolerance?

    <p>To prevent horror autotoxicus</p> Signup and view all the answers

    Where do B cells undergo 'education' in the process of central tolerance?

    <p>Bone marrow</p> Signup and view all the answers

    What is the function of thymic nurse cells in the thymic cortex?

    <p>Providing nutrients to developing thymocytes</p> Signup and view all the answers

    What is the outcome of T cells that fail to bind to MHC molecules during positive selection in the thymic cortex?

    <p>They undergo apoptosis</p> Signup and view all the answers

    What is the primary function of the medullar epithelial cells in the thymic medulla?

    <p>Presenting self-antigen/MHC complexes to T cells</p> Signup and view all the answers

    What is the limitation of central tolerance in preventing autoimmune diseases?

    <p>It is not able to eliminate all self-reactive immune cells</p> Signup and view all the answers

    What is the consequence of low affinity for self-antigens during central tolerance?

    <p>Release of anergic B cells into circulation</p> Signup and view all the answers

    Why is it essential to maintain some self-reactive immune cells in the periphery?

    <p>To regulate tumour surveillance and inflammatory responses</p> Signup and view all the answers

    What is the fate of B cells with high affinity for self-antigens in the bone marrow?

    <p>Deletion by an unknown mechanism</p> Signup and view all the answers

    What is the primary function of central tolerance in T cells?

    <p>To eliminate all self-reactive T cells</p> Signup and view all the answers

    What is the result of weak recognition of self-antigens by B cells in the bone marrow?

    <p>Becoming anergic and released into circulation</p> Signup and view all the answers

    What is the outcome of deleting all self-reactive T cells?

    <p>Severe limitation of the T cell repertoire</p> Signup and view all the answers

    What is the primary function of CTLA-4 in T cells?

    <p>To inhibit T cell responses by binding to CD80/86</p> Signup and view all the answers

    What is the outcome of repeated TCR stimulation in self-reactive T cells?

    <p>Activation-induced cell death (AICD) through Fas and FasL</p> Signup and view all the answers

    Which type of regulatory T cells are generated in the periphery and can be induced by antigen presentation?

    <p>Inducible Tregs</p> Signup and view all the answers

    What is the mechanism of B cell tolerance in chronic infections?

    <p>B cell anergy due to chronic antigen stimulation</p> Signup and view all the answers

    What is the function of FcgR2b in B cells?

    <p>To inhibit B cells and suppress antibody production</p> Signup and view all the answers

    What is the primary mechanism of central tolerance in the thymus?

    <p>Deletion of self-reactive T cells via apoptosis</p> Signup and view all the answers

    What is the outcome of breaking tolerance in the immune system?

    <p>Autoimmune disease and inflammation</p> Signup and view all the answers

    What is the primary mechanism of peripheral tolerance in B cells?

    <p>Anergy of B cells due to chronic antigen stimulation</p> Signup and view all the answers

    What is the association between autoimmune diseases and genetic factors?

    <p>Autoimmune diseases have a complex interplay between genetic and environmental factors</p> Signup and view all the answers

    What is the role of vitamin D deficiency in autoimmune diseases?

    <p>Vitamin D deficiency is a potential environmental trigger that contributes to the development of autoimmune disease</p> Signup and view all the answers

    T cells are ‘educated’ in the bone marrow during central tolerance.

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

    The limitation of central tolerance is that it cannot eliminate all self-reactive T cells.

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

    Negative selection in the thymic medulla results in the activation of T cells with low affinity for self-antigens.

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

    The primary function of cortical epithelial cells is to present self-antigens to T cells during negative selection.

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

    Peripheral tolerance is more effective than central tolerance in preventing autoimmune diseases.

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

    The thymic capsule is involved in the positive selection of T cells in the thymic cortex.

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

    All self-reactive T cells that escape central tolerance are eliminated in the periphery.

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

    Receptor editing in B cells can lead to the deletion of the B cell if the process fails.

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

    Central tolerance can account for all innocuous environmental antigens.

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

    A high affinity for self-antigens in B cells always leads to receptor editing.

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

    Peripheral tolerance is not necessary for maintaining a healthy immune system.

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

    Self-reactive B cells undergo selection only in the thymus.

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

    Some self-antigens are only expressed during early +/- selection in the thymus.

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

    Immunologically privileged sites are normally accessible to T cells.

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

    Tolerance is maintained when self-antigens are present in sufficient quantities to reach the threshold of activation for TCR.

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

    Anergy involves the action of positive co-stimulatory pathways.

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

    Tolerogenic or immature DCs can provide co-stimulation to T cells.

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

    Central tolerance is the primary mechanism of tolerance in the periphery.

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

    CTLA-4 expression is induced upon TCR stimulation and has low affinity for CD80/86.

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

    Repeated activation of the TCR induces expression of anti-apoptotic proteins such as Bcl-2.

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

    Regulatory T cells can directly kill APCs and other T cells via Fas and FasL secretion.

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

    Peripheral tolerance mechanisms include ignorance, anergy, deletion, and the effects of regulatory B cells.

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

    Autoimmune diseases are thought to have a environmental trigger but no genetic component.

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

    HLA-DQ, DR, and other genes are associated with reduced risk of autoimmune diseases.

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

    Vitamin D deficiency is a protective factor against autoimmune diseases.

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

    Breaking tolerance can lead to cancer.

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

    The primary function of CTLA-4 is to enhance TCR signalling.

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

    Central tolerance mechanisms remove all self-reactive T and B cells in the thymus and bone marrow.

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

    Study Notes

    • The immune system maintains a state of 'immunological tolerance' to prevent self-reactive immune cells from triggering autoimmunity, which is achieved through central and peripheral tolerance mechanisms.

    • Central tolerance involves the 'education' of T cells in the thymus and B cells in the bone marrow, where self-reactive cells are removed through apoptosis.

    • In the thymus, T cells undergo positive selection in the thymic cortex, where they are tested for MHC binding, and negative selection in the thymic medulla, where they are presented with self-antigen/MHC complexes and undergo apoptosis if they have high affinity for self antigen.

    • Peripheral tolerance involves multiple mechanisms for B and T cells, including ignorance, anergy, deletion, and the effects of regulatory T cells.

    • T cell peripheral tolerance mechanisms include ignorance, where some self-antigens are hidden or not present in sufficient quantities to trigger an immune response, anergy, where T cells are activated without co-stimulation, deletion, where self-reactive T cells are deleted through apoptosis, and the effects of regulatory T cells, which can suppress or kill self-reactive T cells.

    • B cell peripheral tolerance mechanisms include anergy, where self-reactive B cells are unresponsive to antigen, deletion, where self-reactive B cells are deleted through apoptosis, and exclusion, where partially activated B cells are excluded from lymphoid follicles and cannot develop into mature plasma B cells.

    • Breaking tolerance can lead to autoimmune disease, which occurs when the immune system responds to self-antigens, and can range from organ-specific to systemic diseases.

    • Autoimmune diseases are thought to have a genetic component and an environmental trigger, and usually affect women more than men.

    • Regulatory T cells play a crucial role in maintaining peripheral tolerance, and their dysfunction can contribute to autoimmune diseases.

    • FcgR2b, a receptor with an ITIM motif, can inhibit B cell activation when crosslinked by Ab/Ag complexes, leading to a negative signal.

    • BAFF, a survival factor, is important for B cell survival and can contribute to autoimmune diseases when dysregulated.

    • CTLA-4, a negative regulatory molecule, is induced upon TCR stimulation and can inhibit T cell responses by binding to CD80/86 on APCs.

    • Activation-induced cell death (AICD) can delete self-reactive T cells in the periphery through the expression of death receptors and pro-apoptotic proteins.

    • Mucosal immunity is characterized by specialized structural and cellular features that contribute to immune tolerance and prevent excessive immune responses to innocuous antigens.

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    BMS2045 5a Tolerance, Hypersensitivity & Mucosal Immunity 2024.pdf

    Description

    Test your knowledge of the immune system with this quiz on tolerance, hypersensitivity, and mucosal immunity. Learn about the mechanisms of central and peripheral tolerance, autoimmune diseases, and the different types of hypersensitivity responses. Identify the underlying mechanisms and diseases associated with each.

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