Helper T-cell Activation and Polarization
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Questions and Answers

What happens when a T cell recognizes antigen in the absence of co-stimulation?

  • The T cell produces IL-2
  • The T cell enters the cell cycle
  • The T cell avoids apoptosis
  • The T cell becomes anergic (correct)

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

  • Promotes proliferation and differentiation of activated naive T cells (correct)
  • Inhibits CD28-CD80/86 binding
  • Promotes apoptosis of T cells
  • Upregulates HLA-2 expression

    • Which molecule does IL-2 bind to in an autocrine fashion?

  • CD4
  • CD28
  • IL-2R (correct)
  • CD80/86

    • What is the role of DAMPs and PAMPs in the expression of HLA-2 and costimulators on APCs?

    <p>Increase the expression of HLA-2 and costimulators</p> Signup and view all the answers

    What is the advantage of synthesizing both IL-2 and the high-affinity IL-2R after CD28-CD80/86 binding?

    <p>Avoids apoptosis by upregulating Bcl-2</p> Signup and view all the answers

    When the dendritic cell arrives at the secondary lymphatic organ, it presents the phagocytosed antigen via its HLA-2 to a naïve Th cell. What happens if the TCR on the Th recognizes the antigen?

    <p>The Th cell becomes activated and secretes IL-2</p> Signup and view all the answers

    What are the major Th1 polarizing cytokines that bind to receptors on the activated Th cells?

    <p>IL-12, IL-18, IFN-gamma</p> Signup and view all the answers

    What is the function of the Th1 transcription factor Tbet?

    <p>It activates genes related to Th1 response</p> Signup and view all the answers

    Which cytokines bind to their receptors on the Th cell, leading to activation/production of the Th1 transcription factor?

    <p>IL-12 and IL-18</p> Signup and view all the answers

    What happens when PRRs are activated in dendritic cells?

    <p>Increased expression of HLA-2 and CD 80/86 on the dendritic cell</p> Signup and view all the answers

    What is the role of IL-2 in lymphocyte activation?

    <p>Stimulates the growth and differentiation of T-lymphocytes</p> Signup and view all the answers

    How do Treg cells differ from other types of Th cells?

    <p>Treg cells express the Foxp3 transcription factor</p> Signup and view all the answers

    What is the mechanism of cross-regulation between Th cells?

    <p>Secretion of inhibitory cytokines by one Th cell to control another</p> Signup and view all the answers

    Describe the process of CD8+ cytotoxic T-cell activation.

    <p>Recognition of intracellular antigens presented by Class I MHC molecules</p> Signup and view all the answers

    What is the common role of Th1, Th2, Th9 cells in relation to B-cells?

    <p>Causing formation of antibodies</p> Signup and view all the answers

    What is the primary function of Follicular Th (Tfh) cells in secondary lymphoid organs (SLOs)?

    <p>All of the above</p> Signup and view all the answers

    What is the process known as when B-cells 'reshuffle' their antibodies and select those with very high affinity to reproduce in germinal centers?

    <p>Affinity maturation</p> Signup and view all the answers

    What inhibits Tfh development and likely drives the naive Th to other types such as Th17 and Th1 cells?

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

    Which type of antibodies are produced during the first round of B-cell antibody production when experiencing an infection?

    <p>Low-affinity antibodies with many epitopes</p> Signup and view all the answers

    What is the significance of Tfh cells in the context of B-cell function?

    <p>They enable affinity maturation during antibody production</p> Signup and view all the answers

    Which of the following is the transcription factor for Tfh?

    <p>Bcl6</p> Signup and view all the answers

    What type of cell secretes polarizing cytokines for Th1?

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

    Which of the following Th cells combats intracellular pathogens and activates macrophages?

    <p>Th1</p> Signup and view all the answers

    Which of the following Th cells can be polarized by IL-4?

    <p>Th2</p> Signup and view all the answers

    Which of the following Th cells provide autoimmunity and combat extracellular pathogens?

    <p>Th17 and Th9</p> Signup and view all the answers

    Th1 cells can sometimes stay in lymph nodes to continue activation of other T cells and B cells

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

    Which of the following Th cells activates macrophages?

    <p>Th1</p> Signup and view all the answers

    What is the site of activation and polarization for Th cells?

    <p>All of the above</p> Signup and view all the answers

    Macrophages require 2 signals for activation: IFN-gamma and ________

    <p>CD40L OR cell contact</p> Signup and view all the answers

    IL-4 and TGF-B can activate.....

    <p>Th9</p> Signup and view all the answers

    Dendritic cells are the main secretor of polarizing cytokines in SLOs

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

    Which of following Th cells comprise the "Type 1 response"?

    <p>Th1 and Th17</p> Signup and view all the answers

    Which of the following are polarizing cytokines for Th17?

    <p>All of the above</p> Signup and view all the answers

    Polarization type depends on the APC

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

    Which of the following Th cells activates cytotoxic T cells?

    <p>Th1</p> Signup and view all the answers

    Cytotoxic cells rely only on the signal of Th1 cells to get activated

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

    CD40L plays a role in activating....

    <p>All of the above</p> Signup and view all the answers

    Active effector cytotoxic T cells do not require co-stimulation

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

    Study Notes

    T Cell Recognition and Activation

    • T cells recognizing an antigen without co-stimulation may become anergic, failing to mount an immune response.
    • IL-2 is crucial for T cell activation, promoting proliferation and differentiation.
    • IL-2 binds to CD25 (the high-affinity IL-2 receptor) in an autocrine manner, enhancing T cell growth.
    • DAMPs (Damage-Associated Molecular Patterns) and PAMPs (Pathogen-Associated Molecular Patterns) stimulate antigen-presenting cells (APCs) to express HLA-2 and co-stimulatory molecules.

    Costimulation and T Cell Differentiation

    • Synthesizing IL-2 alongside the high-affinity IL-2R after CD28-CD80/86 engagement enhances T cell survival and responsiveness.
    • When dendritic cells present antigen via HLA-2 to naïve Th cells, TCR recognition leads to Th cell activation and differentiation.
    • Major polarizing cytokines for Th1 cells include IL-12 and IFN-gamma, promoting their development.

    Th1 Cell Function and Cytokine Interactions

    • The Th1 transcription factor T-bet drives the commitment of T cells to the Th1 lineage.
    • Cytokines IL-12 and IFN-gamma stimulate T-bet production, enhancing Th1 responses.
    • Activation of pattern recognition receptors (PRRs) on dendritic cells boosts their antigen presentation capabilities.

    T Cell Subtypes and Mechanisms

    • IL-2 supports the activation and proliferation of lymphocytes, including T cells and B cells.
    • Treg (regulatory T) cells play a role in maintaining immune tolerance and preventing autoimmunity, differing from effector Th cells.
    • Cross-regulation between Th cells involves cytokine signaling that directs differentiation toward specific subsets.

    CD8+ Cytotoxic T Cell Activation

    • CD8+ cytotoxic T cell activation involves recognizing antigen through their TCR and receiving help from Th1 cells.
    • Common roles of Th1, Th2, and Th9 include enhancing B cell function and antibody production.
    • Follicular Th (Tfh) cells primarily assist in B cell activation and differentiation in secondary lymphoid organs (SLOs).

    B Cell Response and Antibody Production

    • B cells undergo affinity maturation in germinal centers, reshuffling antibodies to select for high-affinity variants.
    • Factors inhibiting Tfh development, like certain inflammatory cytokines, drive naïve Th cells toward Th1 or Th17 differentiation.
    • Initially, B cells produce IgM antibodies during the first round of response to an infection, paving the way for class switching later.

    Th Cell Polarization and Activation

    • Tfh cells significantly impact B cell function by promoting differentiation and class switching in germinal centers.
    • The transcription factor for Tfh cells is Bcl-6, instrumental in driving their identity.
    • Dendritic cells are key in releasing polarizing cytokines for Th1 cells, essential for immune responses against intracellular pathogens.

    Immunological Signaling

    • Th1 cells combat intracellular pathogens and activate macrophages by providing necessary cytokines like IFN-gamma.
    • IL-4 can polarize naive Th cells into Th2 cells, which aid in responses against extracellular pathogens and contribute to allergic reactions.
    • Macrophages require two activation signals: IFN-gamma (from Th1 or CD8+ T cells) and additional support from other cytokines.

    Type 1 Response and Th17 Polarizing Cytokines

    • The "Type 1 response" is characterized by Th1 cells, driving responses against intracellular pathogens.
    • Polarizing cytokines for Th17 cells include IL-6, TGF-beta, and IL-1, facilitating their differentiation.
    • The polarization type is influenced by the APC, showcasing the versatility of the immune response.

    Cytotoxic T Cell Activation and Effector Functions

    • Cytotoxic T cells depend primarily on Th1 cell signaling for activation and do not require additional co-stimulation once they are activated.
    • CD40 ligand (CD40L) plays a role in activating B cells and enhancing immune responses by facilitating interactions between B cells and T cells.
    • Active effector cytotoxic T cells can kill target cells effectively without needing further signals once they've been activated.

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    BMS 150 Immunology V - Helper T-cell Activation and Polarization PDF

    Description

    Test your knowledge about the innate immune response with questions about pathogen recognition receptors (PRRs), dendritic cells, and their migration to lymph nodes. Explore the activation of PRRs by viral or intracellular bacterial infections.

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