Humoral Immunity and Antibodies Quiz
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Questions and Answers

Which type of antibody is primarily produced during the secondary antibody response?

  • IgE
  • IgG (correct)
  • IgA
  • IgM

    • What is the primary difference between polyclonal and monoclonal antibodies?

  • Polyclonal antibodies are produced by a single clone of cells, while monoclonal antibodies are produced by multiple clones.
  • Polyclonal antibodies target a single epitope, while monoclonal antibodies target multiple epitopes.
  • Polyclonal antibodies are produced from multiple B cells, while monoclonal antibodies are produced from a single B cell clone. (correct)
  • Polyclonal antibodies are produced in the laboratory, while monoclonal antibodies are produced naturally in the body.

    • What is the role of helper T cells in the antibody response?

  • Helper T cells directly produce antibodies.
  • Helper T cells suppress the production of antibodies.
  • Helper T cells promote the class switch from IgM to other antibody classes (IgG, IgA, or IgE). (correct)
  • Helper T cells recognize and destroy antigen-presenting cells.

    • What is the main characteristic of the primary antibody response?

    <p>Initial production of IgM antibodies followed by a gradual shift to IgG. (A)</p> Signup and view all the answers

    What is the main advantage of using monoclonal antibodies in medical treatments?

    <p>Monoclonal antibodies have a higher affinity for their target antigen, leading to a more specific and effective treatment. (A)</p> Signup and view all the answers

    What does the 'idiotype' refer to, specifically?

    <p>The specific amino acid sequence in the hypervariable regions of antibodies that recognize a specific antigen (D)</p> Signup and view all the answers

    Which of the following is NOT a step involved in the activation of a B cell by a helper T cell?

    <p>Direct interaction between CD40 ligand on the B cell and CD40 on the T cell (D)</p> Signup and view all the answers

    What is the main function of the hinge region in an antibody molecule?

    <p>Provides flexibility for the antibody to bind to different antigens with varying shapes (B)</p> Signup and view all the answers

    Which of the following cytokines are produced by helper T cells to induce B cell proliferation?

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

    What is the role of CXCL13 and CXCR5 in B cell activation?

    <p>They induce the migration of B cells and helper T cells to the boundaries between B and T cell areas in secondary lymphoid tissues (D)</p> Signup and view all the answers

    In which cellular compartment within the lymph node does somatic hypermutation and class switching occur?

    <p>Germinal center (D)</p> Signup and view all the answers

    What is the most common type of light chain found in human immunoglobulin molecules?

    <p>κ (kappa) (A)</p> Signup and view all the answers

    Which of these is NOT a characteristic of the CDR regions of antibodies?

    <p>They are located in the constant region of the antibody molecule (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the role of helper T cells in humoral immunity?

    <p>Helper T cells activate B cells to differentiate into antibody-producing plasma cells. (A)</p> Signup and view all the answers

    What is the primary function of antibodies in humoral immunity?

    <p>Neutralizing and eliminating pathogens. (A)</p> Signup and view all the answers

    Which of the following describes a thymus-independent (TI) antigen?

    <p>An antigen that can stimulate antibody production without T cell help. (C)</p> Signup and view all the answers

    What is the significance of the interaction between CD40L and CD40 in humoral immunity?

    <p>It induces B cell proliferation and differentiation into plasma cells. (A)</p> Signup and view all the answers

    In which of the following locations do B and T lymphocytes come together to initiate humoral immune responses?

    <p>Peripheral lymphoid organs (C)</p> Signup and view all the answers

    What is the role of pattern recognition receptors (PRRs) in antibody responses?

    <p>PRRs can provide additional signals to B cells alongside BCR engagement, enhancing activation. (B)</p> Signup and view all the answers

    What is the main difference between an antibody response to a protein antigen and a non-protein antigen?

    <p>Protein antigens require T cell help for antibody production, while non-protein antigens can stimulate antibody production without T cell help. (A)</p> Signup and view all the answers

    Which of the following processes is NOT involved in the initial stages of antibody formation?

    <p>Release of cytotoxic T lymphocytes (CTLs) to kill infected cells (C)</p> Signup and view all the answers

    Which immunoglobulin class is primarily responsible for mucosal immunity?

    <p>IgA (C)</p> Signup and view all the answers

    Which immunoglobulin subclass is most effective at activating complement?

    <p>IgG3 (B)</p> Signup and view all the answers

    Which immunoglobulin class is involved in allergic reactions of immediate (anaphylactic) type through the release of mediators?

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

    Which immunoglobulin subclass is associated with host defense against encapsulated bacteria?

    <p>IgG2 (A)</p> Signup and view all the answers

    Which immunoglobulin class is primarily found on B cell surfaces where it functions as a receptor for antigen?

    <p>IgD (C)</p> Signup and view all the answers

    Which immunoglobulin class is the most efficient in agglutination, complement fixation, and other antigen-antibody reactions?

    <p>IgM (C)</p> Signup and view all the answers

    Which immunoglobulin class is the main immunoglobulin produced early in the primary immune response and can be produced in a T cell-independent manner?

    <p>IgM (C)</p> Signup and view all the answers

    Which immunoglobulin class has the longest half-life and can cross the placenta?

    <p>IgG (A)</p> Signup and view all the answers

    Which of the following statements about IgG is FALSE?

    <p>IgG is the main immunoglobulin produced early in the primary immune response. (B)</p> Signup and view all the answers

    Which immunoglobulin class is primarily found in secretions such as milk, saliva, and tears?

    <p>IgA (C)</p> Signup and view all the answers

    Which one of the following statements is FALSE regarding the 5 mechanisms of antibody-mediated resistance to infection?

    <p>Antibodies can directly destroy some bacteria. (B)</p> Signup and view all the answers

    Which immunoglobulin class plays a role in parasitic helminth diseases?

    <p>IgE (C)</p> Signup and view all the answers

    Which immunoglobulin class is involved in the process of class switching after antigenic stimulation?

    <p>IgG (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of immunoglobulin G (IgG)?

    <p>IgG is primarily found on the surface of B cells. (A)</p> Signup and view all the answers

    Which immunoglobulin class is involved in the activation of complement through its Fc portion?

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

    Which immunoglobulin class is found in serum as a monomer, as well as larger polymers in low concentration?

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

    Flashcards

    Humoral Immunity

    A type of adaptive immune response mediated by antibodies produced by B lymphocytes.

    B Lymphocytes

    Cells that produce antibodies in the humoral immune response.

    Antibody Response

    The production of antibodies in reaction to antigens, targeting microbes.

    Multivalent Antigens

    Antigens with multiple binding sites that can activate B cells without T cell help.

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    T-dependent Responses

    Immune responses that require helper T cells to activate B cells and produce antibodies.

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    CD40 Ligand

    A protein expressed by activated helper T cells that binds CD40 on B cells, enhancing activation.

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    Thymus Independent Antigens

    Antigens like polysaccharides that can stimulate antibody production without T cell help.

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    Germinal Centers

    Structures formed in lymphoid organs where B cells proliferate and undergo differentiation following activation.

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    BCR internalization

    B Cell Receptor (BCR) binds to the antigen and is internalized for antigen processing.

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    MHC class II

    MHC class II molecules present processed antigens to CD4+ T cells.

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    Chemokines role

    Chemokines like CXCL13 guide the migration of B and T cells in lymphoid tissues.

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    CD40-CD40L interaction

    CD40 ligand on T cells binds CD40 on B cells to stimulate their proliferation.

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    Immunoglobulins (Ig)

    Antibodies are also known as immunoglobulins, crucial for immune response.

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    Hinge region

    The flexible area in immunoglobulins that allows for 3D structure formation.

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    Complementary Determining Region (CDR)

    CDR is the region of antibodies that interacts directly with antigens, providing specificity.

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    ADCC

    Antibody-Dependent Cell Cytotoxicity; a mechanism where antibodies target cells for destruction by immune cells.

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    Monoclonal antibodies

    Identical antibodies made by a single clone of cells or from hybridomas; target specific antigens.

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    IgM antibodies

    The first antibodies produced during an immune response, appearing within days to weeks after exposure.

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    Class switch

    The process by which B cells change from producing one type of antibody (IgM) to another (IgG, IgA, or IgE).

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    Secondary antibody response

    A faster and stronger immune response to a previously encountered antigen, mainly producing IgG antibodies.

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    IgG Structure

    IgG has a flexible hinge region rich in proline, cleavable by enzymes.

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    Papain Digestion

    Papain digestion of IgG yields two Fab fragments and one Fc fragment.

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    Fab Fragment

    Each Fab fragment contains one antigen-binding site.

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    Pepsin Digestion

    Pepsin produces an F(ab’)2 fragment with two antigen-binding sites.

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    IgG Subclasses

    IgG has four subclasses: IgG1, IgG2, IgG3, IgG4.

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    IgM Function

    IgM is the main antibody in the primary immune response, produced early.

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    IgA Role

    IgA is key for mucosal immunity and found in secretions like saliva and milk.

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    IgE Function

    IgE is involved in allergic reactions and fights parasitic infections.

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    IgD Location

    IgD is found on B cell surfaces, acting as an antigen receptor.

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    Class Switching

    Class switching allows antibodies to change their class while retaining specificity.

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    Complement Fixation

    IgG activates complement; IgM is highly efficient at complement fixation.

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    Opsonization Function

    IgG mediates opsonization by binding antigen-antibody complexes to Fc receptors.

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    IgG Half-Life

    IgG has the longest half-life of 23 days among immunoglobulins.

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    IgM Pentamer

    IgM is a pentameric antibody critical for agglutination and complement activation.

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    Study Notes

    Humoral Immunity and Antibodies

    • Humoral immunity, one of two adaptive immune responses, uses secreted antibodies produced by B lymphocytes to eliminate microbes and antigens.
    • Two types of antigens trigger antibody responses:
      • Multivalent microbial antigens can activate B cells through B cell receptors (BCRs) without T cell help.
      • Microbial protein antigens require B cells to present to helper T cells, resulting in T-dependent responses, where helper T cells drive B cell activation.
    • Antibodies bind to extracellular pathogens (bacteria, viruses), neutralizing and eliminating them.
    • Antibody types mediate different microbe elimination mechanisms.
    • Antibody responses to proteins involve antigen processing by B cells and presentation to helper T cells, leading to B/T cell collaboration.

    Antibody Formation and Activation Steps

    • Antigen binding to BCR immunoglobulin initiates antibody production.
    • Internalization and antigen degradation by B cells transform antigen into peptides.
    • MHC class II-peptide complexes are presented on the B cell surface.
    • Helper T cells (CD4+) with prior antigen exposure recognize these complexes.
    • Chemokines (CXCL13) guide B and T cell migration to lymphoid tissue boundaries.
    • CD40L (on T cells) binds CD40 (on B cells), inducing proliferation and differentiation.
    • B cells differentiate into plasma cells or memory cells, and isotype switching occurs.

    Antibody Structure and Types

    • Antibodies (immunoglobulins, Ig) are gamma globulin proteins in serum (20% of total plasma proteins).
    • Basic immunoglobulin structure: two identical heavy (H) chains and two identical light (L) chains (kappa or lambda).
    • Five immunoglobulin isotypes (classes) with distinct heavy chain types: IgM, IgG, IgD, IgA, and IgE.
    • Flexible hinge regions, rich in proline, in IgG and IgA are susceptible to proteolytic enzymes.
    • Antibody digestion by enzymes (e.g., papain, pepsin) yields fragments with specific functions (e.g., antigen-binding sites).

    IgG Antibodies

    • IgG is the most abundant antibody class (85% in adults).
    • Four subclasses (IgG1, IgG2, IgG3, IgG4) with varying functions and properties.
    • IgG1 is the most abundant.
    • IgG2 targets polysaccharides, important for bacteria defense.
    • IgG3 is potent complement activator.
    • IgG4 does not activate complement.
    • IgG plays crucial roles: long half-life, placental transfer, anamnestic response, antigen binding, complement activation, and opsonization.

    IgM Antibodies

    • IgM is the first antibody produced during primary immune responses.
    • Produced independently of T cell help, especially for carbohydrate antigens.
    • Pentameric structure with five antibody units, crucial for agglutination and complement activation.
    • IgM is effective in agglutination, complement fixation, bacterial, and viral defense.
    • Monomeric IgM serves as a receptor on B cell surfaces.
    • Crucial for responses to polysaccharide antigens.

    IgA Antibodies

    • IgA (5-15% of serum immunoglobulins) is important in mucosal immunity.
    • Found in secretions (milk, saliva, tears, respiratory/intestinal/genital tracts).
    • Protects mucosal surfaces from pathogens.
    • Secretory IgA is a dimer with secretory component and J chain.
    • Two subclasses: IgA1 and IgA2.
    • Some bacteria can destroy IgA1, circumventing Ab resistance.

    IgE Antibodies

    • IgE (<1% of serum immunoglobulins) mediates immediate allergic reactions (anaphylaxis).
    • Also involved in parasitic helminth diseases.
    • Serum IgE measurement aids in parasitic infection diagnosis.

    IgD Antibodies

    • IgD is present at low levels in serum, with primarily unknown functions.
    • Found on B cell surfaces as an antigen receptor.
    • Does not bind complement.

    Antibody Production, Specificity and Memory

    • Initial IgM production followed by class switching to IgG, IgA, or IgE.
    • Class switching depends on T cell cytokines and involves changing the constant region.
    • Polyclonal antibodies are mixtures of many different antibodies due to various B-cells.
    • Antibody affinity refers to the strength of individual antibody-antigen interactions.
    • Avidity is the overall strength of multivalent antibody-antigen binding.
    • Monoclonal antibodies are homogeneous antibodies from a single B-cell clone.
    • Hybridomas are laboratory-derived cells to produce monoclonal antibodies.

    Antibody-Mediated Immune Responses

    • Antibodies mediate responses through mechanisms including opsonization, neutralization, toxin neutralization, complement lysis, and antibody-dependant cell cytotoxicity (ADCC).
    • Primary antibody response is characterized by IgM production first.
    • Secondary (anamnestic) response leads to faster, stronger, longer-lasting IgG responses due to memory cells.

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    Description

    Test your knowledge on humoral immunity and the role of antibodies in eliminating pathogens. This quiz covers the mechanisms of antibody formation, activation, and the interactions between B cells and T cells. Explore the different types of antigens and their impact on immune responses.

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