IMM: BLOCK 2: LECTURE 8: T-CELL ACTIVATION AND EFFECTOR FUNCTION
45 Questions
4 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the function of regulatory T cells (Tregs) in the immune response?

  • Suppress the immune response to prevent autoimmunity (correct)
  • Help in the production of antibodies by B cells
  • Promote the activation of all T cells
  • Enhance cytokine production in effector T cells

    • Which mechanism is primarily utilized by cytotoxic CD8 T cells to eliminate infected cells?

  • Secreting cytokines that promote inflammation
  • Producing antibodies against pathogens
  • Initiating T-cell priming in lymph nodes
  • Directly lysing target cells using perforin and granzymes (correct)

    • What role do cytokines play in T cell function?

  • They have no significant role in regulating T cell activities
  • They serve as primary signals to activate T cells
  • They help in the differentiation and activation of T cells (correct)
  • They are only produced by B cells

    • What is the significance of CD40L in T cell interactions?

    <p>It enhances B cell responses through interactions with CD40</p> Signup and view all the answers

    What happens to naive T cells when they recognize an antigen without co-stimulation?

    <p>They enter a state of anergy and become non-responsive</p> Signup and view all the answers

    What is the consequence of T cells being in an anergic state?

    <p>They are unable to respond to their specific antigen.</p> Signup and view all the answers

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

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

    What determines the differentiation pathway a naive T cell takes during activation?

    <p>The cytokine environment.</p> Signup and view all the answers

    What is the role of TH1 CD4 cells in the immune response?

    <p>To induce macrophage activation.</p> Signup and view all the answers

    Which form of receptor is expressed by naive T cells for interleukin-2?

    <p>A unique form not expressed by activated T cells.</p> Signup and view all the answers

    What is the first step in the activation of a naive B cell by a TFH cell?

    <p>The naive B cell binds antigen with its BCR.</p> Signup and view all the answers

    What interaction leads to the expression of CD40L on TFH cells during B cell activation?

    <p>Cognate pair formation with the B cell.</p> Signup and view all the answers

    Which type of CD4 T cell is associated with an anti-inflammatory response?

    <p>TH2</p> Signup and view all the answers

    What is the primary function of regulatory CD4 T cells (Treg)?

    <p>To limit the activities of effector CD4 and CD8 T cells</p> Signup and view all the answers

    How do CD8 T cells induce apoptosis in their target cells?

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

    What is the role of IL-2 in T cell activation?

    <p>It aids in activating naive CD8 T cells when secreted by CD4 T cells</p> Signup and view all the answers

    What two molecules are involved in T cell interactions with antigen-presenting cells (APCs)?

    <p>LFA-1 and CD40L</p> Signup and view all the answers

    Which statement about naive T cell activation is true?

    <p>Naive CD8 T cells can be activated directly by virus-infected cells</p> Signup and view all the answers

    Why do memory T cells decrease L-selectin expression?

    <p>To allow them to home to sites of inflammation instead of lymph nodes</p> Signup and view all the answers

    What is a consequence of interaction between CD40L on T cells and its receptor?

    <p>It enhances the activation of B cells</p> Signup and view all the answers

    What is the function of VLA-4 integrin expressed by effector T cells?

    <p>To allow adhesion to endothelial cells in inflamed tissue</p> Signup and view all the answers

    Which of the following statements about effector CD8 T cells is NOT true?

    <p>They require co-stimulation for activation.</p> Signup and view all the answers

    What important role does IL-17 play in T cell functions?

    <p>It is crucial for the development of T follicular helper cells.</p> Signup and view all the answers

    What is the purpose of the immunological synapse?

    <p>To facilitate T cell activation and signal transduction</p> Signup and view all the answers

    Which of the following signals triggers T cell anergy?

    <p>Recognition of antigen in the absence of co-stimulation</p> Signup and view all the answers

    What role do ITAMs play in the context of T cell activation?

    <p>They facilitate the signaling process during T cell activation</p> Signup and view all the answers

    Which sub-type of CD4+ T cells is primarily responsible for activating macrophages?

    <p>TH1 cells</p> Signup and view all the answers

    Which statement accurately describes a memory T cell?

    <p>A T cell that has previously encountered an antigen and can respond rapidly upon re-exposure</p> Signup and view all the answers

    What indicates that naive T cells cannot respond to their specific antigen?

    <p>They are in an anergic state.</p> Signup and view all the answers

    Which chains are part of the interleukin-2 (IL-2) receptor unique to T cells?

    <p>Alpha, beta, and gamma chains.</p> Signup and view all the answers

    Which factor primarily determines the type of effector CD4 T cell produced from naive CD4 T cells?

    <p>The cytokine environment.</p> Signup and view all the answers

    What is the primary function of TH1 CD4 effector cells?

    <p>Inducing macrophage activation.</p> Signup and view all the answers

    During the activation of a naive B cell, which step follows the binding of the antigen with the B cell receptor (BCR)?

    <p>The antigen is internalized and presented via MHC II.</p> Signup and view all the answers

    How do naive B cells interact with TFH cells during their activation?

    <p>By recognizing the same epitope of the antigen.</p> Signup and view all the answers

    Which aspect of TFH cell activation is critical for the naive B cell function?

    <p>Cognate interaction leading to CD40L expression.</p> Signup and view all the answers

    Which type of helper T cell is characterized as having an anti-inflammatory phenotype?

    <p>TH2 CD4 cells.</p> Signup and view all the answers

    What is required for the activation of naive CD8 T cells when direct activation by a dendritic cell is insufficient?

    <p>Co-stimulation from CD4 T cells</p> Signup and view all the answers

    Which molecule is primarily responsible for effector T cells homing to inflamed tissues?

    <p>VCAM-1</p> Signup and view all the answers

    Which T cell type primarily employs the secretion of IL-2 to facilitate the activation of naive CD8 T cells?

    <p>Effector CD4 T cells</p> Signup and view all the answers

    What characteristic change occurs in memory T cells regarding L-selectin expression?

    <p>Decreased expression to favor different tissue homing</p> Signup and view all the answers

    What type of cytokines do effector T cells primarily release to mediate their functions?

    <p>Cytokines and cytotoxins</p> Signup and view all the answers

    What is the mechanism by which autoreactive Treg cells prevent the proliferation of autoreactive helper CD4 T cells?

    <p>By interacting with the same APC and using cytokine signals</p> Signup and view all the answers

    What role does CD58 play in T cell activation?

    <p>It serves as a backup for co-stimulation in CD8 T cells</p> Signup and view all the answers

    What happens to CD8 T cells that lack CD28 co-stimulation?

    <p>They require CD58 for further activation</p> Signup and view all the answers

    Which cytokine is key in the differentiation of T follicular helper cells that aid in B cell function?

    <p>IL-21</p> Signup and view all the answers

    Study Notes

    T Cell Anergy

    • T cells become anergic when they are unable to respond to their specific antigen.
    • Anergy is a state of non-responsiveness.

    Naive T Cell Activation

    • Activation of naive T cells by antigen is driven by the cytokine interleukin-2 (IL-2).
    • Naive and activated T cells express different forms of the IL-2 receptor.
    • The IL-2 receptor is composed of alpha, beta, and gamma chains, separate from the TCR.

    Naive CD4 T Cell Differentiation

    • Activation of naive CD4 T cells creates five types of effector CD4 T cells.
    • The cytokine environment determines the differentiation pathway a naive T cell takes.

    Effector CD4 T Cell Subtypes

    • TH1 Cells - induce macrophage activation making macrophages microbicidal.
    • TH2 Cells - have an anti-inflammatory phenotype.
    • TFH (Follicular Helper) Cells - recognize different epitopes of the same antigen as naive B cells.
    • Treg Cells - limit the activities of effector CD4 and CD8 T cells.
    • TH17 Cells - promote inflammation and are thought to play a role in autoimmune diseases.

    Naive CD8 T Cell Activation

    • Naive CD8 T cells require stronger activation than naive CD4 T cells.
    • Naive CD8 T cells can be activated directly by a virus-infected dendritic cell.
    • Naive CD8 T cells can be activated indirectly by a dendritic cell with insufficient co-stimulation, helped by CD4 effector T cells.
    • IL-2 secreted by CD4 T cells can act directly on naive CD8 T cells interacting with the same dendritic cell.

    CD8 T Cell Co-stimulation

    • Some CD8+ T cells lack CD28.
    • CD58 acts as a backup for co-stimulation by binding to CD2.

    Effector T Cell Functions

    • Effector CD8 T cells and effector CD4 TH1, TH2, and TH17 cells work at sites of infection.
    • The integrin VLA-4 enables effector T cells to home to inflamed tissue.
    • Effector T cell functions are mediated by cytokines and cytotoxins.

    Cytotoxic CD8 T Cell Activity

    • Cytotoxic CD8 T cells are selective and serial killers of infected target cells.
    • Cytotoxic CD8 T cells kill target cells by inducing apoptosis.

    Memory T Cells

    • Some CD4+ T cells enter a memory state.
    • Memory T cells express CD28, increase some adhesion molecules, but decrease surface expression of L-selectin.
    • Memory CD8+ T cells can also form.

    Immunological Synapse

    • The immunological synapse is formed by T-cell and antigen-presenting cell (APC) interactions.

    T-Cell Signal Transduction

    • T-cell signal transduction is the process by which T cells receive and respond to signals from the environment.
    • This process involves various signaling molecules, including the T-cell receptor (TCR) complex, co-receptors, and co-stimulatory receptors.

    Importance of IL-2

    • IL-2 plays a crucial role in T cell activation, proliferation, and differentiation.
    • IL-2 is a growth factor that promotes the expansion of activated T cells, allowing them to mount a robust immune response.

    Co-Stimulatory Molecules

    • Co-stimulatory molecules are critical for T cell activation and ensure that T cells only respond to antigens presented in the context of an immune response (e.g., infection).
    • CD28 is a major co-stimulatory receptor that binds to CD80 and CD86 on APCs.
    • CD58 is a backup co-stimulatory molecule that can bind to CD2 on T cells.

    Immunological Synapse

    • The purpose of the immunological synapse is to facilitate communication and interaction between T cells and antigen-presenting cells (APCs).

    T-Cell Signal Transduction

    • T-cell signal transduction is the process of transmitting signals from the cell surface to the inside of the cell.
    • ITAMs are signaling motifs that play a significant role in T-cell signaling.
    • Specific signals are needed to activate T cells and initiate their functions.
    • Different signals can trigger anergy (a state of non-responsiveness) or effector function.

    IL-2 Importance

    • IL-2 is a cytokine crucial for the proliferation and differentiation of activated naive T cells.
    • Naive T cells and activated T cells express different forms of the IL-2 receptor.

    CD4+ & CD8+ Maturation

    • CD4+ and CD8+ T cell maturation differ in their activation pathways and roles in the immune response.

    CD4+ Subtypes

    • There are five subtypes of CD4+ T cells:
      • TH1 cells induce macrophage activation.
      • TH2 cells have an anti-inflammatory phenotype.
      • TH17 cells promote inflammation.
      • Treg cells suppress autoreactive T cells.
      • TFH cells help B cells produce antibodies.

    Co-stimulatory Molecules and Signals

    • Co-stimulatory molecules provide secondary signals necessary for T-cell activation.
    • CD28 is a significant co-stimulatory molecule.
    • CD58 acts as a back-up co-stimulatory molecule that binds with CD2.

    Memory T Cells

    • Some CD4+ T cells enter a memory state.
    • Memory T cells express increased CD28 and decreased L-selectin.
    • Memory T cells are more likely to respond rapidly to CD80/86 displayed by APCs.
    • Memory T cells home to sites of inflammation rather than lymph nodes.

    CD8+ Memory Cells

    • CD8+ T cells can also form memory cells.
    • The expression of CD58 is increased in memory T cell connections.

    T Cell Killing

    • T cell killing involves a process of granular exocytosis that releases cytotoxic molecules, such as perforin and granzymes.
    • The release of these molecules leads to apoptosis (programmed cell death) of the target cell.
    • Cytotoxic CD8 T cells can kill multiple infected target cells in succession.
    • Effector T cells utilize integrin VLA-4 to home to inflamed tissues.
    • Co-stimulatory signals are crucial for the activation of naive T cells but not for activating effector T cells.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    BMS 545 Immunology Lecture Notes PDF

    Description

    This quiz explores the concepts of T cell anergy, activation of naive T cells, and the differentiation of naive CD4 T cells into various effector subtypes. It examines the role of cytokines, particularly interleukin-2, in T cell responses and the functions of different CD4 T cell types.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser