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IMSE311: Antibody Structure and Function
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IMSE311: Antibody Structure and Function

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Questions and Answers

What are natural antibodies?

  • Antibodies that facilitate phagocytosis
  • Antibodies that react against antigens from the same species (correct)
  • Antibodies produced in response to an immunogen
  • Antibodies that react against antigens from different species
  • Which type of antibodies react against heterophile antigens?

  • Complement-fixing antibodies
  • Heterophile antibodies (correct)
  • Natural antibodies
  • Immune antibodies
  • What is the primary function of complement-fixing antibodies?

  • To neutralize toxic substances
  • To react against self-antigens
  • To cause lysis of cells and release of biologically active molecules (correct)
  • To facilitate phagocytosis
  • Which type of antibodies are produced in response to an immunogen?

    <p>Immune antibodies</p> Signup and view all the answers

    What is the primary function of opsonins?

    <p>To facilitate phagocytosis</p> Signup and view all the answers

    Which class of immunoglobulin is considered the best opsonin?

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

    What is the primary function of neutralizing antibodies?

    <p>To remove antigenic determinants from microorganisms</p> Signup and view all the answers

    Which type of antibodies are responsible for agglutination reactions?

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

    What is the primary function of precipitins?

    <p>To form insoluble complexes with soluble antigens</p> Signup and view all the answers

    Which type of antibodies are responsible for allergic reactions?

    <p>Allergic antibodies</p> Signup and view all the answers

    Which type of antibody is primarily responsible for neutralizing toxins and viruses?

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

    Which antibody class is considered the most powerful agglutinator of particulate antigens?

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

    Which antibody class is primarily responsible for opsonization and phagocytosis?

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

    Which of the following antibody classes is primarily involved in immediate hypersensitivity reactions?

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

    Which antibody class is considered the first line of defense in mucosal immunity?

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

    Which antibody class is primarily responsible for complement fixation during the primary immune response?

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

    Which antibody class is capable of crossing the placenta and providing passive immunity to the newborn?

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

    Which antibody class is primarily involved in the selection and activation of naive B cells?

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

    Which antibody class is considered the most effective in complement fixation?

    <p>IgG3</p> Signup and view all the answers

    Which antibody class is primarily associated with immunity against polysaccharide antigens?

    <p>IgG2</p> Signup and view all the answers

    Study Notes

    Antibody Structure and Function

    • Antibodies are specific glycoproteins referred to as immunoglobulins, found in blood plasma and many body fluids.
    • Primary function is to combine with antigens, leading to bacterial or viral neutralization.
    • Main humoral element of the adaptive immune response.

    Immunoglobulin (Ig) Classes

    • Divided into 5 major classes based on heavy chain: IgG, IgM, IgA, IgD, and IgE.

    Antibody Binding Sites

    • Each antibody has at least 2 identical sites that bind antigen (valence).
    • Most antibodies are bivalent.

    Properties of Antibodies

    • Protein in nature with high molecular weight.
    • Present in serum/plasma, saliva, semen, CSF, and other body fluids.

    General Functions of Immunoglobulins

    • Neutralize toxic substances.
    • Facilitate phagocytosis and kill microbes.
    • Combine with antigens on cellular surfaces, causing destruction of cells.

    Classification of Antibodies

    • According to sedimentation constant: IgG, IgA, IgM, IgD, and IgE.
    • According to temperature: cold antibodies (IgM) and warm antibodies (IgG).
    • According to occurrence: natural antibodies and immune antibodies.
    • According to reaction with antigen: agglutinins, hemagglutinins, precipitins, and lysins.

    Structure of Immunoglobulin

    • Basic structural unit of an antibody: monomer.
    • Consists of 2 heavy chains and 2 light chains.
    • Heavy chain: gamma, alpha, mu, delta, and epsilon.
    • Light chain: kappa and lambda.

    3-Dimensional Structure of Antibodies

    • Folded into compact globular subunits based on the formation of balloon-shaped loops at each domain.

    Enzyme Digestion

    • Papain digestion: breaks the immunoglobulin molecule in the hinge region, producing Fab and Fc fragments.
    • Pepsin digestion: cleaves the heavy chain after the H-H interchain disulfide bonds, resulting in an F(ab')2 fragment.

    Immunoglobulin G (IgG)

    • Most predominant immunoglobulin.
    • Only antibody that can pass through the placenta, providing immunity to the newborn.
    • Equally distributed in different fluid compartments.
    • Mediates complement fixation and opsonization.

    Immunoglobulin A (IgA)

    • Found in serum in small amounts but predominant in sero-mucous secretions.
    • Provides immunity to the infant digestive tract.
    • Acts as a first line of defense for natural immunity.

    Immunoglobulin M (IgM)

    • Powerful agglutinator of particulate antigen.
    • Does not cross the placenta.
    • First antibodies produced during an infection.
    • Has 10 binding sites (pentamer).

    Immunoglobulin D (IgD)

    • Heat-labile immunoglobulin.
    • Detected by highly sensitive assays requiring radio-labeled antisera.
    • Precise biological action is not known, but may play a role in antigen-triggered lymphocyte differentiation.

    Immunoglobulin E (IgE)

    • Most heat-labile immunoglobulin.
    • Bound to mast cells and basophils throughout the body.
    • Synthesized locally by plasma cells present in the mucous membrane of the GI and respiratory tracts.
    • Associated with immediate hypersensitivity reactions and immunity to certain helminthic parasites.

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    Description

    This quiz covers the topic outline of Antibody Structure and Function, including the Classification of Antibodies, Structure of Immunoglobulin, 3-Dimensional Structure of Antibodies, Enzyme Digestion, Immunoglobulin Classes, and Theories of Antibody Production. Explore the concepts related to antibody structure, function, and binding to various cell types.

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