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Questions and Answers

What is the role of interferons in the immune response?

  • To induce cells to resist viral infections (correct)
  • To promote T-cell proliferation
  • To stimulate antibody production
  • To enhance the action of macrophages

    • Which of the following are primary immune organs in vertebrates?

  • Thymus and Spleen
  • Spleen and lymph nodes
  • Lymph nodes and bone marrow
  • Bone marrow and thymus (correct)

    • What distinguishes type II interferons from type I interferons?

  • They have similar structural properties
  • They are produced by activated lymphocytes (correct)
  • They are primarily involved in antibody activation
  • They only act against bacterial infections

    • How do NK cells collaborate with other immune cells?

    <p>By partnering with macrophages and dendritic cells</p> Signup and view all the answers

    What is a key characteristic of the adaptive immune system?

    <p>It can specifically recognize and remember pathogens</p> Signup and view all the answers

    What are KIR and KAR in the context of immune cell signaling?

    <p>Receptors associated with the adaptive immune system</p> Signup and view all the answers

    What activates the apoptosis pathway in response to viral PAMPs?

    <p>PRR interaction with viral PAMPs</p> Signup and view all the answers

    Which cells primarily produce type I interferons?

    <p>A variety of cells during viral infection</p> Signup and view all the answers

    What type of lymphocytes are primarily found near the central arteriole in the periarteriolar lymphoid sheath (PALS)?

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

    Which component of the lymphoid follicles contains macrophages and differentiating B cells?

    <p>Marginal zone</p> Signup and view all the answers

    What unique characteristic do liver-resident NK cells possess?

    <p>They are unable to leave the liver.</p> Signup and view all the answers

    What is the potential role of the specialized NK cells found in the liver according to Viki Male's research?

    <p>They may act as an early warning system for liver-specific viruses.</p> Signup and view all the answers

    Which of the following statements correctly describes NKT cells in sooty mangabeys?

    <p>They differ from other species in lacking CD4+ NKT cells.</p> Signup and view all the answers

    What is contained in the perifollicular zone surrounding lymphoid follicles?

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

    What major finding regarding NKT cells was presented by Amintinder Kaur?

    <p>SIV-infected mangabeys are protected from NKT cell depletion.</p> Signup and view all the answers

    What distinguishes the T cells in the PALS from the surrounding B cells?

    <p>T cells are mainly situated near the central arteriole while B cells are found peripherally.</p> Signup and view all the answers

    What is the primary function of the innate immune system?

    <p>To express pattern recognition receptors that identify foreign structures</p> Signup and view all the answers

    Which of the following locations is NOT considered a primary lymphoid organ?

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

    How do activated lymphocytes behave in the lymph nodes?

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

    Which type of T lymphocyte assists in B-cell activation?

    <p>CD4+ helper T cells</p> Signup and view all the answers

    What is the role of germinal centers in the lymph nodes?

    <p>Area where B cells mature and undergo affinity maturation</p> Signup and view all the answers

    Which cell type is responsible for attacking and destroying virally infected cells?

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

    How do lymphocytes return to the bloodstream after exiting a lymph node?

    <p>Through the thoracic duct</p> Signup and view all the answers

    What process allows for class switching in B lymphocytes?

    <p>Affinity maturation</p> Signup and view all the answers

    Which organ is a secondary lymphoid tissue responsible for processing antigens from lymphatic fluid?

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

    What happens to lymphocytes that are not activated by specific antigens in lymph nodes?

    <p>They leave in efferent lymph and return to the thoracic duct</p> Signup and view all the answers

    What is the primary function of macrophages in the lymph node?

    <p>To remove pathogens and debris</p> Signup and view all the answers

    What occurs after dendritic cells encounter T-cells in the lymph node?

    <p>Dendritic cells trigger the division of pathogen-specific lymphocytes</p> Signup and view all the answers

    Which type of cell in the lymph node directly stimulates B cells?

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

    Where do plasma cells secrete antibodies after differentiating in the lymph node?

    <p>Into the medulla of the lymph node</p> Signup and view all the answers

    What is the primary function of the spleen regarding pathogens?

    <p>To act as the first line of defense against blood-borne pathogens</p> Signup and view all the answers

    Which part of the spleen is responsible for removing old and damaged red blood cells?

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

    What is the composition of the marginal zone in the spleen?

    <p>Contains specialized macrophages and B cells</p> Signup and view all the answers

    After exiting the lymph node, where do some plasma cells travel to continue antibody secretion?

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

    What is the primary function of NK cells in the innate immune response?

    <p>To kill virally infected and tumor cells</p> Signup and view all the answers

    Which molecules do killer activation receptors (KARs) on NK cells recognize?

    <p>Stress-related molecules</p> Signup and view all the answers

    What is the role of killer inhibition receptors (KIRs) in NK cell function?

    <p>To assess the normality of host cells</p> Signup and view all the answers

    How do NK cells interact with macrophages during an infection?

    <p>NK cells activate macrophage proliferation</p> Signup and view all the answers

    What differentiates Natural Killer T cells (NKT) from conventional T cells?

    <p>NKT cells recognize lipids presented by CD1d</p> Signup and view all the answers

    What is a characteristic of the NK cell memory response?

    <p>NK cells retain memory of encounters with specific pathogens</p> Signup and view all the answers

    Which factor enhances NK cell cytotoxicity at infection sites?

    <p>Type I interferon activation</p> Signup and view all the answers

    What happens to activated NK cells when abundant at infection sites?

    <p>They kill dendritic cells to limit adaptive response</p> Signup and view all the answers

    What process describes how Type 1 immunity protects against intracellular microbes?

    <p>Through the activation of mononuclear phagocytes</p> Signup and view all the answers

    What role do NK cells play in relation to tumor cells?

    <p>They kill tumor cells without prior sensitization</p> Signup and view all the answers

    Study Notes

    Lymphatic System

    • Lymph nodes filter and process antigens in lymphatic fluid
    • Afferent vessels carry lymph into a lymph node
    • Efferent vessels carry lymph out of a lymph node
    • Macrophages remove pathogens and debris within the lymph node
    • Dendritic cells become residents of the lymph node and move to T-cell areas
    • Dendritic cells present antigens to T cells, which then differentiate into effector cells
      • Helper T cells (CD4+) assist in B cell activation
      • Cytotoxic T cells (CD8+) attack infected cells
    • Some effector T cells leave in efferent lymph and travel to infected tissue
    • Other helper T cells stay in the lymph node and stimulate B cell proliferation and differentiation
    • B cells mature in germinal centers and differentiate into plasma cells
      • Plasma cells secrete pathogen-specific antibodies, increasing antibody affinity and possibly switching antibody class
    • Plasma cells move into the medulla of the lymph node or leave to the bone marrow to secrete large quantities of antibodies
    • Antibodies travel to infected tissue via efferent lymph and blood

    Spleen

    • The spleen acts as the first line of defense against blood-borne pathogens
    • It weighs ~150g and is larger than any lymph node
    • Consists of red pulp and white pulp
      • Red pulp: removes old and damaged red blood cells from circulation
      • White pulp: contains white blood cells
        • Marginal zone: specialized area with macrophages and B cells, bordering the white pulp and separating it from the red pulp
    • The spleen has organized aggregations of lymphocytes, similar to those in lymph nodes

    Natural Killer (NK) Cells & Natural Killer T (NKT) Cells

    • NK cells are circulating lymphocytes of the innate immune response
    • They kill virally infected cells and tumor cells without prior sensitization
      • Some virus-infected cells
      • Cells covered with antibody
      • Cells that do not express normal levels of MHC class I molecules
    • NK cells play a role in both innate and adaptive immunity
    • NKT cells are a unique subset of T cells that develop in the thymus
    • NKT cells express a TCR with a very limited repertoire
    • Unlike other T cells, NKT cells respond to lipids, glycolipids, or hydrophobic peptides presented by CD1d and secrete large amounts of cytokines, especially IL-4

    Killer Activation Receptors (KARs) & Killer Inhibition Receptors (KIRs)

    • NK cells don't have antigen-specific receptors like other lymphoid cells
    • KARs recognize stress-related molecules on unhealthy or infected host cells, such as MICA and MICB
      • Binding of MICA or MICB induces NK cell destruction of the target cell
    • KIRs monitor MHC class I molecules on the surface of all nucleated cells
      • MHC class I: present normal antigens
      • Determine if a host cell is healthy
        • If MHC class I is subnormal, the target cell is killed
        • If MHC class I is normal, the target cell is released
    • NK cell cytotoxicity is activated at sites of virus infection
      • Type I interferon induces NK cell proliferation and differentiation

    Interactions Between NK Cells and Other Immune Cells

    • NK cells and macrophages activate each other at sites of infection
      • This interaction induces NK cell proliferation and differentiation
    • NK cells can kill dendritic cells to prevent the activation of adaptive immunity if innate immunity is overcoming the infection
    • When NK cells are scarce and innate immunity cannot control an infection, NK cells induce dendritic cells to migrate to secondary lymphoid tissue to initiate the adaptive immune response
    • NK cell populations retain a memory of previous encounters with pathogens

    Primary and Secondary Lymphoid Organs

    • Primary lymphoid organs: sites where immune cells develop
      • Bone marrow: B cell development
      • Thymus: T cell development
    • Secondary lymphoid organs: sites where the immune response is initiated
      • Lymph nodes: filter and process antigens in lymph
      • Spleen: filters blood-borne antigens
      • Barrier tissues: sites of immune response
    • Tertiary lymphoid organs: organize and maintain immune responses when needed (like in chronic infections)
    • Lymphocyte recirculation:
      • Lymphocytes circulate between blood and lymph, entering lymph nodes through the walls of capillaries
      • Lymphocytes that are not activated by specific antigens leave in the efferent lymph and return to the blood
      • Lymphocytes that are activated by specific antigens stay in the lymph node to divide and differentiate into effector cells

    Adaptive vs. Innate Immunity

    • Innate immunity uses germline-encoded pattern recognition receptors (PRRs), which recognize structures on potentially invasive organisms
    • Adaptive immunity uses somatically generated epitope-specific T cell and B cell receptors (TCRs and BCRs)
    • The immune system must be able to distinguish between its own molecules and cells (self) and foreign molecules (nonself).

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