IMM: BLOCK 2: WEEK 7 REVIEW
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Questions and Answers

What is the primary function of the immunological synapse?

  • To regulate apoptosis in T cells
  • To enhance the release of cytokines only
  • To facilitate communication between T cells and antigen-presenting cells (correct)
  • To eliminate T cells that do not respond to antigens

    • Which co-stimulatory molecule is specifically associated with CD4+ T cells?

  • CD58
  • 4-1BB
  • CD28
  • CD40 (correct)

    • What signals are necessary for T cell activation?

  • Intracellular signaling only
  • First and second signals involving an immunological synapse (correct)
  • Signals from other immune cells only
  • Only cytokines from B cells

    • What role do ITAMs play in T cell signaling?

    <p>They are important for signal transduction upon T cell activation</p> Signup and view all the answers

    How do CD4+ T cells and CD8+ T cells differ in their maturation and activation?

    <p>CD8+ T cells primarily utilize 4-1BB for their activation</p> Signup and view all the answers

    Which cytokine is essential for the proliferation and differentiation of activated naive T cells?

    <p>IL-2</p> Signup and view all the answers

    What happens to CD8+ T cells if they are missing CD28 during activation?

    <p>They can still be stimulated by CD58</p> Signup and view all the answers

    Which of the following statements about memory T cells is true?

    <p>Memory T cells are responsible for providing a rapid response upon re-exposure to the same antigen</p> Signup and view all the answers

    What is the main purpose of the immunological synapse?

    <p>To facilitate communication and signaling between immune cells.</p> Signup and view all the answers

    Which two signals are essential for the activation of naive T cells?

    <p>Antigen-specific signal and co-stimulatory signal.</p> Signup and view all the answers

    What are immunoreceptor tyrosine-based activation motifs (ITAMs)?

    <p>Conserved sequences in TCR responsible for intracellular signaling.</p> Signup and view all the answers

    What triggers tolerance/anergy in T cells?

    <p>First signal only.</p> Signup and view all the answers

    Which structure within the immunological synapse is primarily associated with receptor signaling?

    <p>Central supramolecular activation complex (c-SMAC).</p> Signup and view all the answers

    How do CD4+ and CD8+ T cells differ in their activation processes?

    <p>Both mature the same but become single positive during positive selection.</p> Signup and view all the answers

    What role do co-stimulatory signals play in T cell activation?

    <p>They provide a secondary signal that enhances T cell activation.</p> Signup and view all the answers

    What happens when both the first signal and second signal are delivered along with cytokines?

    <p>The T cells undergo activation and exhibit effector functions.</p> Signup and view all the answers

    What is the primary determinant of whether a thymocyte matures into a CD4+ or CD8+ T cell?

    <p>The interaction of the T-cell receptor with peptide:MHC class II or class I complexes</p> Signup and view all the answers

    How do T cells with high-affinity T-cell receptors (TCRs) for self-MHC/peptide complexes typically respond during negative selection?

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

    Which process allows T cells to leave the thymus and enter peripheral circulation after maturation?

    <p>Positive selection</p> Signup and view all the answers

    What role do ITAMs play in T cell signaling?

    <p>They are involved in the phosphorylation cascade leading to T cell activation</p> Signup and view all the answers

    What triggers the process of anergy in T cells?

    <p>Weak TCR signaling in the absence of co-stimulatory signals</p> Signup and view all the answers

    Which of the following statements correctly compares CD4+ and CD8+ T cell activation?

    <p>CD4+ T cells help activate CD8+ T cells but are not required for their initial activation</p> Signup and view all the answers

    What is the primary function of the immunological synapse?

    <p>To enhance communication between T cells and antigen-presenting cells</p> Signup and view all the answers

    What best describes the 'homing' mechanism of T cells to secondary lymphoid tissues?

    <p>It involves adhesion molecules and chemokines guiding T cells</p> Signup and view all the answers

    Study Notes

    Naive T cell activation

    • After negative selection, T cells are mature and leave the thymus
    • Both CD4+ and CD8+ T cells require a "first" and "second" signal for activation
    • The "first" signal comes from TCR/CD4 and p:MHC class II complex on dendritic cell
    • The "second" signal comes from CD28 co-stimulatory receptor & B7 (CD80/86)
    • *CD40 & CD40L are key co-stimulatory molecules for CD4+ cells
    • *4-1BB & 4-1BBL are key co-stimulatory molecules for CD8+ cells
    • CD58 can also stimulate CD8+ T cells if CD28 is missing
    • The first signal alone leads to tolerance/anergy
    • First + second signal = Activation
    • First + second signal + cytokines = Effector function
    • If only the first signal is received, the T cell becomes tolerant, or anergic, and cannot be activated.
    • The immunological synapse forms between a naive T cell and a dendritic cell
    • It includes a central (c-SMAC) and peripheral (p-SMAC) supramolecular activation complex (c-SMAC)
    • The c-SMAC mainly contains signaling molecules and the p-SMAC mainly contains adhesion molecules

    Signal transduction

    • The TCR and CD4 co-receptor bind to the p:MHC class II complex on the dendritic cell, delivering the first signal for T cell activation
    • The CD28 co-stimulatory receptor on the T cell binds to the B7 (CD80/86) co-stimulator on the dendritic cell, delivering the second signal for T cell activation
    • ITAMs (immunoreceptor tyrosine-based activation motifs) are conserved sequence that are repeated twice in the cytoplasmic tails of the TCR.
    • They initiate intracellular immune signaling and activation of immune cells
    • IL-2 is a cytokine that drives proliferation and differentiation of activated naive T cells

    CD4+ and CD8+ T cell Maturation and Activation

    • Both CD4+ and CD8+ T cells mature in the thymus and become single positive during positive selection
    • CD4+ cells mature and differentiate into various subsets based on their role with different cytokine production
    • The most important subtypes are TH1, TH2, TH17, Treg and Tfh
    • CD8+ cells differentiate into cytotoxic T lymphocytes (CTLs)
    • Their activation and differentiation depend on antigen presentation and cytokine signaling
    • CD8+ cells are able to kill infected cells that present viral or tumor antigens

    Immunological synapse

    • It is an ordered structure that functions as an immunological synapse
    • The immunological synapse is formed when two immune system cells bind with receptors and adhesion molecules
    • It allows the exchange of signals and the secretion of effector molecules

    Homing & Trafficking

    • Homing refers to the process of T cells migrating from the thymus to secondary lymphoid tissues
    • Lymphocyte trafficking is the movement of lymphocytes between different tissues
    • They are regulated by chemokines, adhesion molecules and homing receptors that are expressed on the surfaces of lymphocytes
    • T cells use chemokines to find their way to lymph nodes where they can encounter antigens.
    • chemokines are specific for different lymphoid organs, providing precise guidance for homing.

    Dendritic cell maturation and antigen presentation

    • Dendritic cells act as antigen-presenting cells (APCs)
    • They capture antigens and present them to T cells
    • Maturation is a process that increases their ability to present antigens
    • It involves changes in expression of MHC molecules, co-stimulatory molecules, and chemokine receptors
    • During maturation, dendritic cells migrate from the tissues to the lymph nodes, where they can activate T cells

    Memory T cells

    • They are long-lived T cells that can rapidly respond to a re-exposure to a specific antigen
    • They are generated from activated naive T cells during an immune response
    • They provide long-term protection against pathogens

    Importance and Significance of IL-2

    • Interleukin-2 (IL-2) is a crucial cytokine that regulates T cell proliferation, differentiation, and survival
    • It is mainly secreted by T cells (CD4+ and CD8+)
    • It has different functions depending on the context and the stage of T cell activation
    • IL-2 promotes the expansion of antigen-specific T cells
    • It contributes to the establishment of memory T cells
    • It also contributes to the suppression of immune responses

    Central tolerance

    • Ensures that T cells do not attack self-antigens or other antigens in the body
    • It is established during thymic T cell development
    • It is mainly mediated by negative selection
    • It prevents the development of autoimmune diseases

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    Immunology Week 7 Review

    Description

    This quiz covers the intricate process of naive T cell activation, focusing on the critical signals required for their activation, including the roles of TCR/CD4, MHC class II, and various co-stimulatory molecules. Understand the significance of the immunological synapse and how the first and second signals influence T cell behavior. Test your knowledge on the activation pathways essential for T cell function in the immune response.

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