Cells and Organs of the Immune System Chapter 2
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Questions and Answers

Where does hematopoiesis occur in the body?

  • Liver
  • Bone marrow (correct)
  • Spleen
  • Kidneys

    • Which cells are involved in the immune system?

  • Neutrophils
  • Platelets
  • Lymphocytes (correct)
  • Erythrocytes

    • Which organ is considered part of the lymphoid system?

  • Stomach
  • Small intestine
  • Pancreas
  • Thymus (correct)

    • Where does hematopoiesis begin in humans?

    <p>Embryonic yolk sac</p> Signup and view all the answers

    What is the origin of all blood cells?

    <p>Hematopoietic Stem Cells (HSC)</p> Signup and view all the answers

    What is the defining characteristic of stem cells?

    <p>Ability to regenerate or 'self-renew'</p> Signup and view all the answers

    Which type of cell does a stem cell differentiate into early in hematopoiesis?

    <p>Lymphoid progenitor cell</p> Signup and view all the answers

    What is the defining characteristic of progenitor cells during hematopoiesis?

    <p>They have lost the capacity for self-renewal</p> Signup and view all the answers

    What happens to stem cells during the development of the lymphoid and myeloid lineages?

    <p>They differentiate into progenitor cells</p> Signup and view all the answers

    Which cells give rise to lymphoid and myeloid progenitors?

    <p>Hematopoietic stem cells</p> Signup and view all the answers

    From where do all lymphoid cells descend?

    <p>Lymphoid progenitor cells</p> Signup and view all the answers

    Where do some dendritic cells come from during hematopoiesis?

    <p>Lymphoid progenitors</p> Signup and view all the answers

    What is the average lifespan of a RBC (Erythrocyte)?

    <p>120 days</p> Signup and view all the answers

    How long can WBCs (Leukocytes) live?

    <p>From few days to 20-30 years</p> Signup and view all the answers

    What is hematopoietic homeostasis?

    <p>A continuous process maintaining a steady state in blood cell production and loss</p> Signup and view all the answers

    What is one way in which steady-state regulation of hematopoiesis is accomplished?

    <p>Control of the levels and types of cytokines produced by bone-marrow stromal cells</p> Signup and view all the answers

    Which cell types produce cytokines with hematopoietic activity?

    <p>Activated T cells and macrophages</p> Signup and view all the answers

    What is regulated in stem cells and progenitor cells to influence hematopoiesis?

    <p>Expression of receptors for hematopoietically active cytokines</p> Signup and view all the answers

    Which morphologic changes are associated with cells undergoing programmed cell death?

    <p>Decrease in cell volume, modification of the cytoskeleton, chromatin condensation, DNA degradation</p> Signup and view all the answers

    Which process leads to the release of cell contents and may induce a local inflammatory response?

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

    Which type of cell death does not induce a local inflammatory response?

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

    What percentage of the body’s white blood cells do lymphocytes constitute?

    <p>20%–40%</p> Signup and view all the answers

    Which cells are responsible for adaptive immunity and immunologic diversity?

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

    What is the predominant cell type in the lymph?

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

    What is the defining characteristic of naïve lymphocytes?

    <p>They have not interacted with antigen</p> Signup and view all the answers

    How are different lineages or maturational stages of lymphocytes distinguished?

    <p>By their expression of membrane molecules recognized by particular monoclonal antibodies</p> Signup and view all the answers

    What are blast cells called when they interact with antigen and proliferate?

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

    Naïve lymphocytes have not interacted with antigen.

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

    Lymphoblasts are 15μm-diameter blast cells.

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

    All monoclonal antibodies that react with a particular membrane molecule are grouped together as a cluster of differentiation (CD).

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

    What is the phase of the cell cycle in which resting (naive or unprimed) lymphocytes reside?

    <p>G0 phase</p> Signup and view all the answers

    What do B and T lymphocytes enlarge into after antigen activation?

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

    At what stage can B and T lymphocytes not be distinguished morphologically?

    <p>Resting (naive or unprimed) stage</p> Signup and view all the answers

    Where do B cells mature in birds?

    <p>Bursa of fabriscus</p> Signup and view all the answers

    What distinguishes mature B cells from other lymphocytes?

    <p>Synthesis and display of membrane-bound immunoglobulin</p> Signup and view all the answers

    What is the fate of memory B cells?

    <p>Longer life span with the same membrane-bound antibody as parent B cell</p> Signup and view all the answers

    Where do T lymphocytes (T cells) mature?

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

    What is the main site of antigen recognition for T cells?

    <p>Cell membrane</p> Signup and view all the answers

    Which subpopulation of T cells generally functions as T cytotoxic (Tc) cells?

    <p>CD8+ T cells</p> Signup and view all the answers

    Which receptor do Natural Killer (NK) cells express that allows them to attach to antibodies and subsequently destroy targeted cells?

    <p>CD16</p> Signup and view all the answers

    What is the primary function of Natural Killer (NK) cells in the innate immune response?

    <p>Recognize tumor or virus-infected cells</p> Signup and view all the answers

    Which type of lymphocyte is large, granular, and involved in the innate immune response?

    <p>Innate lymphoid cells (ILCs)</p> Signup and view all the answers

    Which cells do not express clonally distributed receptors for antigens but participate in initiating lymphocyte responses to antigens?

    <p>Mononuclear phagocytes and dendritic cells</p> Signup and view all the answers

    Which cells originate in the bone marrow, circulate in the blood, and mature into macrophages in various tissues?

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

    What are the cells that settle in tissues, mature, and become macrophages?

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

    What is the fate of the digested antigen after phagocytosis?

    <p>Eliminated through exocytosis</p> Signup and view all the answers

    What enhances phagocytosis?

    <p>Antibody attached to the antigen</p> Signup and view all the answers

    What happens to some of the digested antigen after phagocytosis?

    <p>Presented on the membrane on MHC</p> Signup and view all the answers

    Where are follicular dendritic cells (FDCs) primarily found?

    <p>Germinal centers of lymphoid follicles in the lymph nodes and spleen</p> Signup and view all the answers

    Which type of dendritic cells has long membranous extensions resembling dendrites on nerve cells?

    <p>Langerhans DC</p> Signup and view all the answers

    What is the primary role of dendritic cells in the immune system?

    <p>Induction of T lymphocyte responses to protein antigens</p> Signup and view all the answers

    Which leukocyte is the first to arrive at the site of inflammation?

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

    Which leukocyte plays a role in parasitic organism defense?

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

    Which leukocyte plays a role in allergic reactions?

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

    Where do mature lymphocytes interact with antigens in the immune system?

    <p>Lymph nodes, spleen, and mucosa-associated lymphoid tissues</p> Signup and view all the answers

    Which organs are considered primary lymphoid organs responsible for the maturation of lymphocytes?

    <p>Thymus and bone marrow</p> Signup and view all the answers

    What is the function of gut-associated lymphoid tissues (GALT) in the immune system?

    <p>Trapping antigen and providing sites for mature lymphocytes to interact with that antigen</p> Signup and view all the answers

    Primary organs of the immune system are thymus and bone marrow.

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

    Once mature lymphocytes have been generated in the primary lymphoid organs, they circulate in the blood and lymphatic system.

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

    Lymph nodes, spleen, and mucosa-associated lymphoid tissues are examples of secondary organs of the immune system.

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

    Bone marrow is the site of generation of all circulating blood cells.

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

    T cells mature in the thymus.

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

    The function of the thymus includes generating and selecting a repertoire of T cells to protect the body from infection.

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

    Where does hematopoiesis occur mostly?

    <p>Iliac bones</p> Signup and view all the answers

    What is the primary function of the thymus?

    <p>Generate and select a repertoire of T cells</p> Signup and view all the answers

    Where do immature B cells proliferate and differentiate?

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

    What is the primary function of the thymus?

    <p>Produce and select a repertoire of T cells to protect the body from infection</p> Signup and view all the answers

    Where do T cells mature?

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

    What decreases with age?

    <p>Thymus function</p> Signup and view all the answers

    Where is interstitial tissue fluid carried into progressively larger lymphatic vessels?

    <p>Tissue spaces</p> Signup and view all the answers

    What is the fluid called after it leaves the lymph nodes?

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

    Where does the lymph finally drain into the circulatory system?

    <p>Thoracic duct or right lymph duct</p> Signup and view all the answers

    Where are immune responses initiated?

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

    Which region of the lymph node contains T helper cells and dendritic cells?

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

    What is the primary cell type found in the medulla of the lymph node?

    <p>Plasma cells</p> Signup and view all the answers

    Where are old and defective red blood cells destroyed and removed?

    <p>Red pulp of the spleen</p> Signup and view all the answers

    Which type of lymphocytes are mainly populated in the PALS (periarteriolar lymphoid sheath) of the white pulp in the spleen?

    <p>T lymphocytes</p> Signup and view all the answers

    Through which vessel are blood-borne antigens and lymphocytes carried into the spleen?

    <p>Splenic artery</p> Signup and view all the answers

    Where are Peyer’s patches found?

    <p>In the walls of the small intestine</p> Signup and view all the answers

    Which organ defends against antigens entering through nasal and oral epithelial routes?

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

    Where are the adenoids located?

    <p>In the roof of the nasopharynx</p> Signup and view all the answers

    Where are M cells located?

    <p>Mucous membranes</p> Signup and view all the answers

    What is the main function of Peyer's patches in the intestine?

    <p>To constitute a nodule of lymphoid follicles</p> Signup and view all the answers

    Where is the antigen released after being transported across M cells?

    <p>Large basolateral pocket</p> Signup and view all the answers

    Where does antigen transportation across the epithelial layer by M cells take place?

    <p>Gut-associated lymphoid tissues (GALT)</p> Signup and view all the answers

    What do activated B cells differentiate into after being activated in the underlying lymphoid follicles?

    <p>IgA-producing plasma cells</p> Signup and view all the answers

    What is the primary characteristic of intraepithelial lymphocytes in the outer mucosal epithelial layer?

    <p>Many are CD8 T cells expressing TCRs with limited receptor diversity for antigen</p> Signup and view all the answers

    Which cells are primarily responsible for inducing a local inflammatory reaction in the skin?

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

    What type of cells in the skin can express class II MHC molecules and function as antigen-presenting cells?

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

    What is the main function of the epidermal layer of the skin in nonspecific (innate) defenses?

    <p>Acting as an anatomic barrier to the external environment</p> Signup and view all the answers

    What is the defining characteristic of a secondary follicle?

    <p>Contains a ring of B cells surrounding germinal center</p> Signup and view all the answers

    What comprises a primary follicle?

    <p>Network of follicular dendritic cells and small resting B cells</p> Signup and view all the answers

    What happens to a primary follicle after antigenic activation?

    <p>It transforms into a secondary follicle</p> Signup and view all the answers

    Which vertebrates lack B and T cells and cannot mount adaptive immune responses?

    <p>Jawless fishes</p> Signup and view all the answers

    What do jawed vertebrates possess that jawless fishes lack?

    <p>B and T cells</p> Signup and view all the answers

    What is the primary characteristic of a secondary lymphoid follicle?

    <p>Large germinal center surrounded by a dense mantle of small lymphocytes</p> Signup and view all the answers

    What causes phagocytes and lymphocytes to leave the blood stream and enter the affected area during an infection?

    <p>Chemotactic signals</p> Signup and view all the answers

    How do distant sites ensure activation of T cells and B cells in response to infection?

    <p>Antigen arrival at lymph nodes via lymph and dendritic cells</p> Signup and view all the answers

    What brings lymphocytes and other leukocytes to the site of infection?

    <p>Inflammatory processes</p> Signup and view all the answers

    Chemotactic signals are generated that can cause phagocytes and lymphocytes to leave the blood stream and enter the affected area.

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

    Inflammatory processes bring only lymphocytes to the site of infection.

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

    Antigen from distant sites can arrive at lymph nodes via lymph and dendritic cells, thereby assuring activation of T cells and B cells.

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

    Study Notes

    Hematopoiesis

    • Occurs in the body mainly in the bone marrow
    • Involves the development of all blood cells from hematopoietic stem cells

    Immune System

    • Involves lymphoid cells, including B cells and T cells, which originate from hematopoietic stem cells
    • Key players: B cells, T cells, natural killer cells, dendritic cells, macrophages

    Hematopoietic Stem Cells

    • Define characteristic: ability to self-renew and differentiate into multiple cell types
    • Early in hematopoiesis, differentiate into myeloid or lymphoid progenitor cells
    • Give rise to lymphoid and myeloid progenitors, which develop into different blood cells

    Progenitor Cells

    • Defining characteristic: ability to differentiate into specific cell types
    • During hematopoiesis, proliferate and differentiate into mature blood cells

    Lymphoid and Myeloid Lineages

    • Develop from hematopoietic stem cells
    • Lymphoid lineage: gives rise to lymphoid cells (B cells, T cells, natural killer cells)
    • Myeloid lineage: gives rise to myeloid cells (red blood cells, platelets, granulocytes, monocytes)

    Blood Cells

    • Red blood cells (erythrocytes): average lifespan of 120 days
    • White blood cells (leukocytes): lifespan varies, some can live for years, others for only a few days
    • Platelets: lifespan of 7-10 days

    Lymphocytes

    • Constitute 20-40% of white blood cells
    • B cells: responsible for adaptive immunity and immunologic diversity
    • T cells: mature in the thymus, involved in cell-mediated immunity
    • Naïve lymphocytes: have not interacted with antigen, reside in G0 phase of the cell cycle
    • Activated lymphocytes: enlarge and proliferate after antigen interaction

    Dendritic Cells

    • Originate from hematopoietic stem cells
    • Primary role: antigen presentation to T cells
    • Found in lymphoid organs, skin, and other tissues

    Phagocytosis

    • Process by which cells engulf and digest foreign particles and antigen
    • Enhances phagocytosis: opsonins, complement system
    • Fate of digested antigen: some is presented to T cells, some is destroyed

    Immune Response

    • Initiated in secondary lymphoid organs (lymph nodes, spleen, mucosa-associated lymphoid tissues)
    • Involves interaction between antigen-presenting cells, T cells, and B cells
    • Chemotactic signals attract phagocytes and lymphocytes to sites of infection

    Lymphoid Organs

    • Primary lymphoid organs: bone marrow, thymus
    • Secondary lymphoid organs: lymph nodes, spleen, mucosa-associated lymphoid tissues
    • Functions: maturation of lymphocytes, activation of immune responses

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    Description

    Test your knowledge on hematopoiesis, cells of the immune system, organs of the immune system, and evolutionary comparisons of lymphoid cells and organs. This quiz covers key concepts in immunology and hematopoiesis.

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