Immunology Basics: Antigens and Antibodies
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Questions and Answers

What is the primary role of antibodies in the immune response?

  • Facilitating the clonal deletion of T cells
  • Directly attacking pathogens
  • Producing antigens
  • Neutralizing pathogens and aiding their removal (correct)

    • Which immunoglobulin class is primarily responsible for the first response to bacterial infections?

  • IgA
  • IgD
  • IgE
  • IgM (correct)

    • How do haptens differ from traditional antigens?

  • Haptens are proteins only.
  • Haptens are not immunogenic unless bound to a larger molecule. (correct)
  • Haptens can stimulate T cells directly.
  • Haptens are usually larger than antigens.

    • What is the function of plasma cells in the immune system?

    <p>To secrete antibodies (C)</p> Signup and view all the answers

    Which statement best describes the difference between primary and secondary immune responses?

    <p>Secondary responses are stronger and faster than primary responses. (D)</p> Signup and view all the answers

    What is an epitope?

    <p>A specific site on an antigen that is recognized by antibodies. (D)</p> Signup and view all the answers

    In which part of the body do B lymphocytes mature?

    <p>Bone marrow (D)</p> Signup and view all the answers

    Which type of T cell is directly involved in killing infected or cancerous cells?

    <p>Cytotoxic T cells (C)</p> Signup and view all the answers

    Which immunoglobulin class has a role in mucosal immunity and is found in secretions such as saliva and breast milk?

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

    What is the primary mechanism of action for antibodies involved in opsonization?

    <p>Coating pathogens to enhance phagocytosis (B)</p> Signup and view all the answers

    Which statement correctly describes the primary response compared to the secondary immune response?

    <p>The secondary response produces antibodies more rapidly compared to the primary response. (D)</p> Signup and view all the answers

    What is the main characteristic of haptens that differentiates them from larger antigens?

    <p>Haptens are too small to be immunogenic by themselves. (D)</p> Signup and view all the answers

    In which part of the body do T lymphocytes undergo maturation?

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

    Which feature is characteristic of both B cells and T cells during an immune response?

    <p>Both are capable of clonally expanding upon activation. (D)</p> Signup and view all the answers

    What is the role of major histocompatibility complex (MHC) molecules in the immune system?

    <p>They bind non-self antigens and present them to T cells. (D)</p> Signup and view all the answers

    What distinguishes IgM from other immunoglobulin classes?

    <p>It is the first antibody class produced during an immune response. (B)</p> Signup and view all the answers

    Flashcards

    Antigen

    A substance that triggers an immune response.

    Protein vs. Polysaccharide Antigens

    Proteins are stronger immune triggers, while polysaccharides are weaker.

    Epitope

    A specific region of an antigen that is recognized by an antibody.

    Hapten

    A small molecule that is not immunogenic on its own.

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    Immunoglobulin (Antibody)

    A protein that binds specifically to an antigen.

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    Antigen-Antibody Reactions (ex: Neutralization)

    Antibodies neutralize pathogens by blocking their ability to infect cells.

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    B-lymphocyte Maturation

    B lymphocytes mature and develop in the bone marrow.

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    Clonal Selection

    The process where specific B and T cells multiply in response to an antigen or pathogen.

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    What makes a substance an antigen?

    An antigen is a foreign molecule that triggers an immune response. It must be large enough (>10,000 molecular weight), be non-self, and have specific regions (epitopes) that bind to antibodies.

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    What is an epitope?

    An epitope is a specific region on an antigen molecule that binds to an antibody. It's like a small 'handle' or 'lock' that an antibody recognizes.

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    How do antibodies neutralize pathogens?

    Antibodies neutralize pathogens by binding to their surface, blocking their ability to infect cells, or neutralizing toxins they produce.

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    Where do B cells mature?

    B cells mature in the bone marrow, where they learn to recognize and respond to specific antigens.

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    What are B cell/T cell clones?

    B and T cell clones are identical cells that recognize the same antigen. During an immune response, specific clones multiply to fight the infection.

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    Study Notes

    Antigen Characteristics

    • Antigens are substances that trigger an immune response.
    • Proteins are stronger antigens than polysaccharides.
    • Must be large (molecular weight > 10,000), non-self, and degradable.
    • Antigens have specific reactive sites called epitopes.
    • Antibodies (immunoglobulins) have complementary reactive sites called paratopes.
    • Small molecules (haptens) become immunogenic when combined with body proteins.

    Immunoglobulins (Antibodies)

    • Immunoglobulins are globular proteins.
    • They have specific reactions with antigens:
      • Neutralization of pathogens
      • Opsonization for phagocytosis
      • Agglutination
      • Complement activation
      • Antibody-dependent cell-mediated cytotoxicity

    Lymphocyte Maturation

    • B lymphocytes mature in the bone marrow.
    • T lymphocytes mature in the thymus.

    Antibody Classes (Immunoglobulins)

    • IgG: Most abundant (80%), crosses placenta, antitoxin, divalent.
    • IgM: Pentamer, first made, highly antibacterial, decavalent.
    • IgA: Secretory, found in fluids (mucus, saliva, tears, breast milk), 10-15%
    • IgD: 0.5%
    • IgE: 0.002%, binds to mast cells/basophils, triggers allergic reactions.
    • Each class has a different function and half-life.

    B Cell Function

    • Plasma cells are antibody-producing factories.
    • B memory cells provide long-term immunity.
    • Clonal selection determines which B cells respond to a specific antigen.
    • Clonal deletion removes potentially harmful B cell clones.

    T Cell Function

    • Helper T cells assist B cells in response to antigens.
    • Cytotoxic T cells (Tc) kill infected or cancerous cells using perforins and granzymes.
    • Natural killer T (NK) cells directly attack non-self cells.
    • Thymus is the maturation site

    Immune Responses

    • Primary response: takes 7-10 days to produce protective antibodies, IgM first then IgG.
    • Secondary (memory) response: quicker and stronger (1-2 days), higher antibody production.
    • Booster shots (vaccinations) stimulate a secondary response.

    Antigen-Antibody Reactions

    • Agglutination: clumping of antigens.
    • Opsonization: coating of antigens to enhance phagocytosis.
    • Neutralization: blocking of harmful effects of antigens.
    • Complement activation: cascade of proteins to enhance immune response.
    • Antibody-dependent cell-mediated cytotoxicity: antibodies mark cells for destruction.

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    Description

    Test your knowledge on the characteristics of antigens and immunoglobulins. This quiz covers essential concepts such as the structure of antibodies, lymphocyte maturation, and the various classes of immunoglobulins. Perfect for students studying immunology or related fields.

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