Lec 6 Quiz
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Questions and Answers

Which of the following accurately describes the roles of primary and secondary lymphoid organs?

  • Primary lymphoid organs respond to antigens in the blood, while secondary lymphoid organs respond to antigens in the tissues.
  • Primary lymphoid organs are where immune responses occur, while secondary lymphoid organs are involved in immune cell development.
  • Primary lymphoid organs are sites of immune cell development and education, while secondary lymphoid organs are where immune responses are initiated. (correct)
  • Primary lymphoid organs filter antigens from tissues, while secondary lymphoid organs educate immune cells.

    • How does lymph circulate through the lymphatic system, considering it lacks a central pump?

  • Lymph is moved through the lymphatic vessels via peristaltic contractions of the vessel walls.
  • Lymph is circulated by the pressure gradient created by the heart's pumping action.
  • Lymph is propelled by the action of cilia lining the lymphatic ducts.
  • Lymph circulation relies on muscle contractions and body movement to propel the fluid through the vessels. (correct)

    • What is the primary purpose of 'Clusters of Differentiation' (CD) markers in immunology?

  • To measure the overall health and activity of the lymphatic system.
  • To serve as targets for therapeutic drugs and to identify and characterize cell surface proteins. (correct)
  • To identify and classify different types of pathogens.
  • To directly neutralize and eliminate foreign antigens from the body.

    • What is the most significant mechanism that generates the vast diversity of B cell receptors (BCRs) and T cell receptors (TCRs)?

    <p>Genetic recombination of different gene segments. (C)</p> Signup and view all the answers

    Which statement best describes the process of clonal selection and expansion in adaptive immunity?

    <p>Lymphocytes with receptors that recognize a specific pathogen are stimulated to proliferate and differentiate into effector cells. (D)</p> Signup and view all the answers

    How does the function of a B cell receptor (BCR) differ from that of an antibody?

    <p>A BCR is membrane-bound and involved in initial antigen recognition, while an antibody is secreted and neutralizes pathogens. (B)</p> Signup and view all the answers

    Where do T-cells undergo education?

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

    Which of the following is an example of a secondary lymphoid organ that is encapsulated and filters antigens from the blood?

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

    Flashcards

    Primary lymphoid organs

    Organs responsible for the education of lymphocytes, including thymus and bone marrow.

    Secondary lymphoid organs

    Organs that facilitate immune responses, including lymph nodes and spleen.

    Lymphatic system

    Network of organs and vessels that transport lymph, crucial for immune function.

    Lymph

    Colorless fluid containing white blood cells, draining through lymphatics into the bloodstream.

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    Cluster of differentiation (CD)

    Naming system for cell surface proteins, used as biomarkers for cell identification.

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    BCR vs Antibody

    BCR is membrane-bound on B cells; antibody is the soluble form secreted by plasma cells.

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    Clonal selection

    Process where specific lymphocytes that recognize a pathogen are selected and proliferate.

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    BCR and TCR diversity

    BCRs and TCRs' extreme variability creates diverse adaptive immunity.

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    Study Notes

    Primary and Secondary Lymphoid Organs

    • Primary lymphoid organs are responsible for the education of lymphocytes.
    • The thymus and bone marrow are primary lymphoid organs.
    • Secondary lymphoid organs are involved in immune responses to antigens.
    • Encapsulated organs like lymph nodes (react to antigens in tissues) and the spleen (reacting to antigens in blood) are secondary.
    • Unencapsulated organs like mucosa-associated lymphoid tissue (MALT) (reacting to antigens at mucosal surfaces) are also secondary.

    Lymphatic System

    • The lymphatic system is a network of organs, nodes, ducts, and vessels, moving lymph from tissues to the bloodstream.
    • Lymph is a colorless fluid containing white blood cells that bathes tissues.
    • The lymphatic system is crucial for the immune system.
    • Lymph is moved through the system by muscle contractions and body movements.
    • Lymph nodes are small, round structures strategically located, filtering lymph and trapping pathogens (bacteria, viruses, toxins), cancer cells.
    • The spleen filters blood, removing old/damaged red blood cells and contains white pulp for secondary lymphoid function.

    Cluster of Differentiation (CD)

    • Cell surface proteins' identities were previously unknown.
    • CD followed by a number is used to identify cell surface proteins.
    • CDs are biomarkers for cell differentiation.
    • CD expression can be cell and tissue-specific.

    BCRs, Antibodies, and TCRs Diversity

    • BCRs and TCRs exhibit high variability, essential for adaptive immunity's diversity.
    • BCR (B Cell Receptor) antigen-binding site is formed by the light and heavy chains.
    • TCR (T Cell Receptor) antigen-binding site is formed by the alpha and beta chains.

    Clonal Selection and Expansion

    • Adaptive immunity depends on the selection and expansion of B and T cells recognizing pathogens.
    • Lymphocytes are initially generated with diverse receptors.
    • Specific pathogen-reactive lymphocytes are stimulated to divide and proliferate.
    • Pathogen-activated lymphocytes become effector cells to fight pathogens.

    BCRs vs. Antibodies

    • BCRs are membrane-bound on B cells, initiating antigen recognition.
    • Antibodies are soluble forms of BCRs, secreted by plasma cells.
    • Antibodies neutralize pathogens, facilitate pathogen destruction, and activate the complement system.

    Antibody Structure / Digestion by Papain

    • Antibodies (and BCRs) are composed of four subunits: two heavy (H) chains and two light (L) chains.
    • Each chain has variable regions for antigen binding and constant regions determining the antibody class.
    • Disulfide bonds connect the chains.
    • Papain digestion creates:
      • Two Fab fragments (Fragment antigen-binding), each with an antigen-binding site, lacking effector functions.
      • One Fc fragment (Fragment crystallizable), responsible for immune cell and complement protein interaction.

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    Description

    This quiz covers the primary and secondary lymphoid organs, including their roles in the immune system. It explores the structure and function of the lymphatic system, detailing how lymph is transported and filtered through various organs. Test your knowledge on the key components and functions crucial for immune responses.

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