Fundamentals of Immunology - Humoral Immunity
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Questions and Answers

What are the two main types of adaptive immunity?

Humoral immunity and cell-mediated immunity.

What type of cells produce antibodies?

  • Macrophages
  • Plasma cells (correct)
  • B lymphocytes
  • T lymphocytes

    • What do antibodies recognize?

    Microbial antigens

    What is the function of the Fab region of an antibody?

    <p>Binding to antigens (D)</p> Signup and view all the answers

    Which of the following is NOT a function of antibodies?

    <p>Cell division (B)</p> Signup and view all the answers

    What is the main function of IgG antibodies?

    <p>Neutralization, opsonization, and activation of complement.</p> Signup and view all the answers

    The complement system is part of the adaptive immune system.

    <p>False (B)</p> Signup and view all the answers

    Which of the following mechanisms describes how antibodies enhance killing of pathogens that are too large to be phagocytosed?

    <p>Antibody-dependent cell-mediated cytotoxicity (ADCC) (D)</p> Signup and view all the answers

    What are the three main ways antibodies provide immunity?

    <p>Preventing pathogen entry, stimulating removal, and triggering destruction of pathogens.</p> Signup and view all the answers

    Flashcards

    Humoral Immunity

    Immune response mediated by antibodies produced by B cells.

    B Lymphocytes

    White blood cells that mature in bone marrow and produce antibodies.

    Plasma Cells

    Differentiated B cells that produce and secrete antibodies.

    Memory B Cells

    Long-lived B cells that remain after infection, ready to respond to future exposures.

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    B Cell Activation

    Process triggered by antigens leading to B cell proliferation and differentiation.

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    B Cell Receptors (BCRs)

    Surface molecules on B cells that bind to specific antigens.

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    T Cell-Independent Activation

    B cell activation without T cell assistance, mainly by polysaccharides.

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    T Cell-Dependent Activation

    B cell activation requiring interaction with T helper cells.

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    Linked Recognition

    Coordination between T cells and B cells recognizing the same antigen.

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    Class Switching

    Process where B cells change the class of antibody produced.

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    Neutralization

    Antibodies prevent pathogens from entering or harming cells.

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    Agglutination

    Clumping of pathogens by antibodies to facilitate removal.

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    Opsonization

    Binding of antibodies to pathogens enhancing phagocytosis.

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    ADCC (Antibody-Dependent Cell-Mediated Cytotoxicity)

    Killing of large pathogens by immune cells aided by antibodies.

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    Complement Activation

    Process that enhances inflammatory response and pathogen destruction.

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    Immunoglobulins (Ig)

    Proteins that function as antibodies in the immune response.

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    IgG

    The most common antibody, involved in secondary immune responses.

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    IgM

    First antibody produced during an immune response, pentamer structure.

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    IgA

    Found in mucosal areas and secretions, protects surfaces exposed to foreign substances.

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    IgD

    Membrane-bound antibody found on B cell surfaces, role in activation.

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    IgE

    Involved in allergic reactions and protection against parasites.

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    Antibody Structure

    Antibodies consist of heavy and light chains forming a Y-shape.

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    Fab Region

    Part of the antibody that binds specifically to antigens.

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    Fc Region

    Part of the antibody that activates immune responses.

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    MHC II

    Molecule that presents antigens to T cells during B cell activation.

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    Germinal Center

    Site in lymph nodes where B cells mature and proliferate.

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    Cytokines

    Chemical messengers secreted by T cells to activate B cells.

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    Immune System Components

    Include innate immunity (immediate) and adaptive immunity (specific).

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    Study Notes

    Fundamentals of Immunology - Humoral Immunity

    • Humoral immunity is mediated by antibodies produced by activated B cells
    • Antibodies recognize microbial antigens, neutralizing infectivity and targeting microbes for degradation
    • The development of plasma cells and memory B cells is divided into three stages:
      • Generation of mature, immunocompetent B cells (maturation)
      • Activation of mature B cells when interacting with antigens
      • Proliferation and differentiation of activated B cells into plasma cells and memory B cells
    • B cells accumulate at specific sites known as germinal centers (white pulp of spleen and cortex of lymph nodes).
    • Humoral immunity involves the activation of B cells into plasma cells.
    • Plasma cells produce antibodies, releasing them into blood and lymphatic fluids to execute their functions.

    B-Cell Receptors (BCRs)

    • BCRs are antigen-specific receptors.
    • They have a "Y" shape with two identical heavy chains and two identical light chains, joined by disulfide bonds.
    • BCRs have two antigen-binding sites, allowing binding of specific pathogen epitopes to initiate the activation process.
    • BCRs can interact with epitopes on free antigens or intact pathogens.
    • Importantly, BCRs do not require antigen presentation by MHC molecules.

    Activation of B Cells

    • B cell activation happens through diverse mechanisms, depending on the antigen's molecular class.
    • T-cell-independent activation:
      • Direct binding to polysaccharides, lipopolysaccharides, and non-protein antigens
      • No antigen processing and presentation to T cells
    • T-cell-dependent activation:
      • B cells function as antigen-presenting cells (APCs), presenting processed protein epitopes with MHC class II to helper T cells.

    T-Cell-Independent (TI) Activation of B Cells

    • Repetitive epitopes on a pathogen's surface heavily cross-link BCRs on the B cell.
    • TI activation results in B cell activation, maturation and the production of short-lived plasma cells primarily producing IgM.
    • No memory B cell production is involved, and subsequent exposures do not generate a secondary response

    T-Cell-Dependent (TD) Activation of B Cells

    • Activation can occur in response to:
      • Free protein antigens
      • Protein antigens associated with intact pathogens
    • Internalized antigens are processed and presented with MHC class II molecules on the B cell surface.
    • Helper T cells recognize the presented antigen via their T cell receptor (TCR) and CD4 molecules interacting with MHC class II on the B cell.
    • This linked recognition process is crucial for B cell activation and class switching.
    • Activated helper T cells secrete cytokines that activate B cells, leading to clonal expansion and differentiation into plasma cells.

    Proliferation and Differentiation of B Cells

    • Activated B cells divide rapidly (proliferate) and differentiate.
    • Some activated B cells become plasma cells, producing large amounts of antibodies.
    • Additionally, activated B cells form memory B cells which stay in the body to recognise the antigen again, allowing for a rapid response in future encounters.

    Antibody Structure

    • Antibodies are specific proteins produced by plasma cells.
    • Consist of four polypeptide chain: Two identical heavy chains and two identical light chains (held together by disulfide bonds).
    • Have a Y-shaped structure containing two functional regions:
      • Fab (Fragment antigen-binding): Variable region binds specifically to an antigen's epitope
      • Fc (Fragment crystallizable): Constant region determines antibody class, complement activation and cell binding

    Five Kinds of Antibodies

    • IgG, IgM, IgA, IgD, IgE
    • Variations exist in structure, class switching possibilities and location of action

    How Antibodies Work

    • Antibodies provide immunity by:
      • Preventing pathogen entry/damage (Neutralization)
      • Promoting pathogen removal by macrophages/other cells (Opsonization)
      • Triggering pathogen destruction (complement activation)

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    Related Documents

    Humoral Immunity PDF

    Description

    This quiz covers the essential aspects of humoral immunity, focusing on the role of antibodies and B cells. You'll explore the development stages of plasma cells and memory B cells, as well as the function of B-cell receptors. Test your knowledge on how humoral immunity effectively neutralizes pathogens.

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