Humoral Immune Response Quiz
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Questions and Answers

What is the primary function of the humoral immune response?

  • To activate T lymphocytes
  • To produce memory cells
  • To eliminate extracellular pathogens and prevent spread of intracellular pathogens (correct)
  • To eliminate intracellular pathogens only

    • What triggers the first signal needed for naïve B cell activation?

  • Recruitment of macrophages
  • Abolition of self-receptor binding
  • Binding of an antigen to the B cell receptor (correct)
  • Co-stimulatory signal from helper T cells

    • During clonal selection, what happens to B lymphocytes that carry receptors for self molecules?

  • They undergo class switching
  • They proliferate and produce antibodies
  • They become activated and migrate to lymph nodes
  • They are deleted from the pool of mature naïve B lymphocytes (correct)

    • Which immunoglobulin receptors do naive B cells commonly express?

    <p>IgD and IgM</p> Signup and view all the answers

    What is the role of activated helper T cells in B cell activation?

    <p>They provide the co-stimulatory signal</p> Signup and view all the answers

    What is a result of clonal selection in B lymphocytes?

    <p>Proliferation into a clone of B cells specific to the antigen</p> Signup and view all the answers

    Which type of pathogens does the humoral immune response specifically target?

    <p>Extracellular pathogens such as bacteria</p> Signup and view all the answers

    What is the primary outcome after a B cell has been fully activated?

    <p>They differentiate into plasma cells</p> Signup and view all the answers

    What is the first step in B cell activation by helper T cells?

    <p>B cell presents the antigen with class II MHC molecules</p> Signup and view all the answers

    What cytokines do activated helper T cells produce to stimulate B cells?

    <p>IL-4, IL-5, IL-6, IL-10</p> Signup and view all the answers

    Which antibody is initially secreted by activated B cells?

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

    What distinguishes thymus-independent antigens from thymus-dependent antigens?

    <p>They do not require T cell help for B cell activation.</p> Signup and view all the answers

    What is a significant feature of the response generated by thymus-independent antigens?

    <p>Only IgM antibodies are produced.</p> Signup and view all the answers

    Which factor is critical for the activation of naïve T cells by B cells?

    <p>Binding of CD28 on the T cell to B7 on the B cell</p> Signup and view all the answers

    What is the main role of memory B cells formed after B cell activation?

    <p>To confer long-lasting immunity upon re-exposure to the same antigen</p> Signup and view all the answers

    What is the nature of the antigens that typically activate B cells without T cell assistance?

    <p>Large polymers with repeated epitopes</p> Signup and view all the answers

    What type of antigen requires T cell help for B cell activation?

    <p>Thymus-Dependent Antigen</p> Signup and view all the answers

    Which type of B cell response is absent in Thymus-Independent Antigens?

    <p>Memory B cell response</p> Signup and view all the answers

    What is the main immunoglobulin produced in response to Thymus-Independent Antigens?

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

    What interaction is essential for immunoglobulin class switching?

    <p>CD40 on B cells and CD40L on T cells</p> Signup and view all the answers

    Which cytokine is known to enhance IgE production during class switching?

    <p>IL-4</p> Signup and view all the answers

    What occurs during the primary immune response when encountering an antigen for the first time?

    <p>Lag period before antibodies are detected</p> Signup and view all the answers

    After T cell activation, which immunoglobulin class is typically produced in high levels?

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

    What type of antigen typically consists of large non-peptide polymers with repeated epitopes?

    <p>Thymus-Independent Antigen</p> Signup and view all the answers

    What is the main antibody produced during the primary immune response?

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

    How long does it typically take for antibodies to become detectable in the secondary immune response?

    <p>A few hours to a day</p> Signup and view all the answers

    What is the primary antibody produced during the secondary immune response?

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

    What type of B cell responds during the secondary immune response?

    <p>Memory B cell</p> Signup and view all the answers

    What is the duration of antibody presence in the primary immune response?

    <p>Short, declining rapidly</p> Signup and view all the answers

    Which antibody is predominantly produced when antigens enter the body via mucosal routes?

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

    How does the antibody concentration in the secondary immune response compare to the primary response?

    <p>Higher, about 10 times greater</p> Signup and view all the answers

    Which immunogens typically induce the primary immune response?

    <p>All immunogens</p> Signup and view all the answers

    Study Notes

    Humoral Immune Response

    • The humoral immune response targets extracellular pathogens like bacteria and prevents the spread of intracellular pathogens.
    • Antibodies produced by B lymphocytes are the key players in this response, reacting specifically to antigens that triggered their production.

    Clonal Selection

    • During embryonic development, a vast pool of B lymphocytes forms.
    • Each naïve B lymphocyte carries a unique receptor (BCR) capable of recognizing and binding to a specific antigen.
    • When an antigen enters the body, it selects the B lymphocyte with the matching receptor, binding to it and prompting proliferation.
    • This leads to the creation of a clone (family) of B cells, specifically targeting that antigen.
    • These selected B cells differentiate into plasma cells and secrete antibodies specific to the antigen.
    • B lymphocytes that recognize self-molecules are eliminated at an early stage, preventing autoimmune reactions.

    Steps of Naïve B Cell Activation

    • Mature, naïve antigen-specific B cells migrate from bone marrow to peripheral lymphoid tissues like lymph nodes, where they encounter their specific antigens.
    • Antigen binding to the B cell receptor (IgM and IgD) triggers the first activation signal.
    • The second signal, known as the co-stimulatory signal, is provided by activated helper T cells (mainly Th2).
    • To receive the second signal, the B cell engulfs the bound antigen, processes it, and presents it on its surface associated with class II MHC molecules.
    • This peptide-MHC complex is recognized by antigen-specific helper T cells, leading to the release of:
      • CD40L, which binds to CD40 on the B cell.
      • Cytokines like IL-4, IL-5, IL-6, and IL-10, stimulating the B cell.
    • Following receipt of both signals, the B cell undergoes activation, proliferates, and differentiates into effector plasma cells secreting antigen-specific antibodies.
    • Initially, IgM is secreted, but the cell can switch to producing other antibody isotypes with the same antigen specificity.
    • Some activated B lymphocytes become memory cells, providing a rapid response upon re-exposure to the antigen.

    Thymus-Dependent and Thymus-Independent Antigens

    • Thymus-Dependent (TD) Antigens:
      • Require T cell help for B cell activation.
      • Typically proteins, such as bacterial toxins.
      • Can induce antibody class switching to IgG, IgA, and IgE.
      • Generate strong memory B cell responses.
    • Thymus-Independent (TI) Antigens: - Activate B cells directly without T cell cooperation. - Typically large polymers with repeating epitopes, like capsular polysaccharides. - Result in only IgM production and no class switching. - Do not generate memory B cell responses.

    Immunoglobulin Class Switching (Isotype Switching)

    • During an immune response, plasma cells switch from producing IgM to other immunoglobulin classes like IgG, IgA, or IgE.
    • This switching involves DNA rearrangement and RNA splicing, altering the constant domains of the heavy chain (CH) without affecting the antigen specificity.
    • Switching requires interaction between CD40 on B cells and CD40L on T cells.
    • Cytokines released by T cells determine the antibody isotype produced.

    Primary and Secondary Antibody Response

    • Primary Immune Response:
      • Occurs during the initial encounter with an antigen.
      • Has a lag of approximately 7-10 days for antibody production.
      • Mainly produces IgM, which peaks in 1-2 weeks and rapidly declines.
    • Secondary Immune Response:
      • Triggered by re-exposure to the same antigen.
      • Rapid response due to memory cells generated during the primary response.
      • Primarily produces IgG, with higher concentrations and longer persistence.
      • Exhibits higher antibody affinity and a stronger response.
      • Can be boosted by further antigen exposure.

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    Humoral Immune Response PDF

    Description

    Test your understanding of the humoral immune response, focusing on the role of B lymphocytes and antibodies. This quiz covers the concepts of clonal selection and activation of naïve B cells and their crucial function in targeting pathogens. Prepare to explore the intricate mechanisms of immune defense!

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