Cells and Organs of the Immune System - Introduction to Immunology
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Questions and Answers

What type of cells protect surfaces like skin and gut against extracellular bacteria?

  • Neutrophils
  • Th17 cells (correct)
  • Cytokines
  • Tregs cells

    • Which type of cells monitor and inhibit the activity of other T cells?

  • Th17 cells
  • Cytokines
  • Tregs cells (correct)
  • Neutrophils

    • What are receptors and ligands fundamental for in cellular communication?

  • Activating neutrophils
  • Cellular communication (correct)
  • Enhancing cytokine production
  • Inhibiting immune responses

    • What are molecules that activate receptors called?

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

    Which small proteins have diverse functions like cell growth and activation in immune cell communication?

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

    Which receptors are essential for innate immune-cell activation and inflammatory responses?

    <p>Toll-like receptors</p> Signup and view all the answers

    What is the function of Major Histocompatibility Complex (MHC) proteins?

    <p>Present antigens on cell surfaces</p> Signup and view all the answers

    Which complement proteins punch small holes into pathogens?

    <p>C3a</p> Signup and view all the answers

    What do B-cell receptors (BCRs) recognize?

    <p>Foreign antigens</p> Signup and view all the answers

    In the clinical case presented, what led to the resolution of lymphadenopathy in the cat?

    <p>Antibiotic treatment</p> Signup and view all the answers

    What type of cells express T-cell receptors (TCRs)?

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

    What is the function of the round sac located just before the cloaca?

    <p>Maturation of B lymphocytes</p> Signup and view all the answers

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

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

    What is the primary function of lymph nodes in the immune system?

    <p>Filtering blood for blood-borne antigens</p> Signup and view all the answers

    Which type of spleen tissue is responsible for immune induction?

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

    Where are Peyer's Patches (PP) typically located in the body?

    <p>Small Intestine</p> Signup and view all the answers

    What is the main role of dendritic cells in secondary lymphoid organs?

    <p>Trap and process antigens</p> Signup and view all the answers

    What is the function of Peyer's Patches?

    <p>Initiate the immune response in the intestines</p> Signup and view all the answers

    Which of the following is NOT a component of Mucosal-Associated Lymphoid Tissue (MALT)?

    <p>Ocular-associated lymphoid tissue (OALT)</p> Signup and view all the answers

    Which lymphoid tissue is considered the best-known mucosal-associated lymphoid tissue?

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

    What clinical presentation might be expected in an animal with a high level of Mucosal-Associated Lymphoid Tissue (MALT)?

    <p>Swollen superficial cervical and mandibular lymph nodes</p> Signup and view all the answers

    Which of the following is NOT a function of Gastrointestinal-associated lymphoid tissue (GALT)?

    <p>Filtering blood</p> Signup and view all the answers

    When do Peyer's Patches typically develop in rabbits and rodents?

    <p>2-4 weeks after birth</p> Signup and view all the answers

    What is the primary function of neutrophils in the immune system?

    <p>To circulate in the bloodstream and phagocytose foreign objects</p> Signup and view all the answers

    Which type of cell is responsible for initiating the adaptive immune response?

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

    What is the primary function of B cells in the immune system?

    <p>To produce antibodies to specific antigens</p> Signup and view all the answers

    What is the role of CD8+ T cells in the immune system?

    <p>To recognize and kill infected or cancer cells</p> Signup and view all the answers

    What is the primary function of mast cells in the immune system?

    <p>To produce histamine and mediate allergic reactions</p> Signup and view all the answers

    What is the primary function of eosinophils in the immune system?

    <p>To release toxic substances from their granules and fight infection</p> Signup and view all the answers

    What is the role of natural killer cells in the immune system?

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

    What is the role of monocytes/macrophages in the immune system?

    <p>To present antigens to lymphocytes and coordinate immune response</p> Signup and view all the answers

    Which type of immunity is characterized by a rapid response to infection and does not involve the production of antibodies?

    <p>Innate immunity</p> Signup and view all the answers

    Which type of cell is responsible for presenting antigens to lymphocytes and coordinating the adaptive immune response?

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

    Where are lymphoid cells mainly produced in older fetuses and adults?

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

    What is the main function of primary lymphoid organs?

    <p>Regulation of lymphocyte development</p> Signup and view all the answers

    Which lymphoid organ is involved in the maturation of T lymphocytes?

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

    What happens to thymocytes that bind strongly to self-antigens?

    <p>They undergo negative selection.</p> Signup and view all the answers

    Which type of cells leave the thymus as mature T lymphocytes after passing the selection processes?

    <p>The positively selected cells</p> Signup and view all the answers

    What is the primary function of the Bursa of Fabricius in birds?

    <p>Development of B lymphocytes</p> Signup and view all the answers

    What is the primary function of Gastrointestinal-associated lymphoid tissue (GALT)?

    <p>To carry out the majority of immune responses in the intestines</p> Signup and view all the answers

    Where are Peyer's Patches (PP) typically located in the body?

    <p>In the intestinal mucosa</p> Signup and view all the answers

    What distinguishes Mucosal-Associated Lymphoid Tissue (MALT) from other lymphoid tissues?

    <p>MALT is encapsulated</p> Signup and view all the answers

    Which lymphoid tissue is considered the best-known mucosal-associated lymphoid tissue?

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

    What function does Peyer's Patches serve in rabbits and rodents?

    <p>Immune responses in the intestinal mucosa</p> Signup and view all the answers

    What are the main characteristics of Mucosal-Associated Lymphoid Tissue (MALT)?

    <p>It comprises non-encapsulated lymphoid aggregates dispersed on mucosal surfaces</p> Signup and view all the answers

    Which cells are responsible for recruiting neutrophils to protect surfaces like skin and gut against extracellular bacteria?

    <p>Th17 cells</p> Signup and view all the answers

    Which type of cells have the primary function of monitoring and inhibiting the activity of other T cells?

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

    Which small proteins with diverse functions are involved in immune cell communication?

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

    Which molecules activate receptors in immune cell communication, and can be either free-floating or membrane-bound?

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

    What allows immune cells to dispatch specific instructions tailored to the situation at hand in cellular communication?

    <p>Expression and density of various receptors and ligands</p> Signup and view all the answers

    What is the primary function of the complement system in the immune response?

    <p>To directly kill pathogens by punching small holes into them</p> Signup and view all the answers

    Which cell type is responsible for recognizing general microbial patterns and activating innate immune responses?

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

    Which immune system component is responsible for presenting antigens on cell surfaces and signaling whether a cell is a host cell or a foreign cell?

    <p>Major histocompatibility complex (MHC)</p> Signup and view all the answers

    What type of antibody response was observed in the presented clinical case of the cat with lethargy and swollen lymph nodes?

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

    Which immune cells are primarily responsible for recognizing foreign antigens and initiating the adaptive immune response?

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

    What is the primary role of lymph nodes in the immune system?

    <p>To filter lymph and activate immune responses</p> Signup and view all the answers

    What is the function of the structure that undergoes involution and contains lymphocytes and plasma cells in its cortex?

    <p>Maturation of B lymphocytes</p> Signup and view all the answers

    Which type of tissue undergoes involution and contains densely packed lymphoid follicles with only B lymphocytes?

    <p>Peyer's Patches</p> Signup and view all the answers

    Which lymphoid organ filters blood for blood-borne antigens and cellular debris and stores red blood cells and platelets?

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

    Which secondary lymphoid organ is responsible for the interaction between dendritic cells and T and B lymphocytes?

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

    Which tissue is composed of a network of connective tissue trabeculae and consists of red and white pulp?

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

    Which secondary lymphoid organ is found in the wall of the small intestines and undergoes involution in young ruminants?

    <p>Peyer's Patches</p> Signup and view all the answers

    Study Notes

    Immune System

    • The immune system is a network of cells, tissues, and organs that work together to defend the body against infections and diseases.

    Cells of the Innate Immunity

    • Granulocytes:
      • Neutrophils: most numerous innate immune cells (50-70% of all white blood cells), produced in bone marrow, circulate in bloodstream, and migrate to tissue to phagocytose and degrade bacteria.
      • Eosinophils: important for host defense against parasites and allergic reactions, differentiated from myeloid precursor cells in response to IL-3, IL-5, and GMCSF.
      • Basophils: involved in host defense against parasites and allergic reactions, contain toxic granules used to destroy pathogens.
    • Mast cells: similar to basophilic leukocytes, found in tissues, important for defense against parasites, and mediate allergic reactions.
    • Monocytes/Macrophages:
      • Found in blood and tissues, coordinate immune response, notify other immune cells of infection.
      • Present antigens to lymphocytes, have important non-immune functions (e.g., recycling dead cells).
    • Natural Killer cells:
      • Phagocytic, cytotoxic cells that recognize and kill virus-infected cells or tumor cells.
      • Have receptors that recognize MHC class I molecules.
    • Dendritic cells:
      • Professional antigen-presenting cells, capture, process, and present antigens to T cells.
      • Classified as classical/conventional dendritic cells (cDCs) and plasmacytoid dendritic cells (pDCs).

    Cells of the Adaptive Immunity

    • B cells (B lymphocytes):
      • Produce antibodies, essential for humoral immune response.
      • Mature in bone marrow (birds: Bursa of Fabricius), activated when binding antigens through their receptors (BCR).
    • T cells (T lymphocytes):
      • Express antigen-specific receptor (TCR), divided into two categories: CD8+ T cells and CD4+ T cells.
      • CD8+ T cells (cytotoxic T cells): recognize and kill infected or cancer cells.
      • CD4+ T cells: divided into four subsets (Th1, Th2, Th17, and T regulatory cells).

    Organs of the Immune System

    • Lymph nodes:
      • Filter lymph to trap antigens, contain two important regions: outer cortex and inner medulla.
      • Contain dendritic cells that trap and process antigens, present to lymphocytes.
    • Spleen:
      • Large encapsulated organ, filters blood for blood-borne antigens, cellular debris, and aged blood cells.
      • Stores red blood cells, platelets, and recycles iron.
    • Mucosal-Associated Lymphoid Tissue (MALT):
      • Scattered throughout mucosal surfaces, includes Gastrointestinal-associated lymphoid tissue (GALT), Bronchial-associated lymphoid tissue (BALT), Nasal-associated lymphoid tissue (NALT), and Conjunctiva-associated lymphoid tissue (CALT).
      • GALT is the best known mucosal-associated lymphoid tissue, inductive site of intestinal immune response, and effector site of intestinal immune response.

    Clinical Correlation

    • The observed lymphadenopathy was lymphadenitis, a result of the bacterial infection as well as the cat's immune response to the bacterium.### Lymphoid Cells and Organs

    • Lymphoid cells are first produced in the yolk sac, fetal omentum, and liver, and later in bone marrow in older fetuses and adults.

    • Bone marrow is a hematopoietic organ that gives rise to all blood cells.

    Primary Lymphoid Organs

    • Primary lymphoid organs are where lymphocytes develop and mature.
    • Examples of primary lymphoid organs include bone marrow, thymus, and Bursa of Fabricius in birds.
    • Thymus is located in the thoracic cavity in front and below the heart and is large in newborns but small to invisible in adult animals.
    • The thymus has a cortex with thymocytes (lymphocytes) and a medulla with few lymphocytes.
    • The thymus has no lymphatic vessels leaving it.

    Thymus Function

    • The thymus is responsible for the maturation of T lymphocytes.
    • T lymphocytes learn to recognize self-antigens in the thymus.
    • Thymocytes with receptors that bind strongly to self-antigens are destroyed through apoptosis (negative selection).
    • Thymocytes that cannot bind any MHC II molecules are also removed.
    • Thymocytes that recognize MHC II/Ag complexes with moderate affinity are allowed to live (positive selection).

    Bursa of Fabricius

    • The Bursa of Fabricius is found in birds only.
    • It is a primary lymphoid organ where B lymphocytes develop and mature.

    Secondary Lymphoid Organs

    • Secondary lymphoid organs are where lymphocytes interact with microbial antigens.
    • Examples of secondary lymphoid organs include spleen, lymph nodes, non-encapsulated lymphoid tissue, and Peyer’s patches.
    • Secondary lymphoid organs develop late in fetal life and persist in adult life.
    • They enlarge in response to antigenic stimulation.

    Lymph Nodes

    • Lymph nodes are round-shaped or bean-shaped encapsulated organs.
    • They act as filters of lymph to trap antigens.
    • They contain two important regions: the outer cortex and inner medulla.
    • The cortex has germinal centers with B lymphocytes, surrounded by capsules.
    • T cells and dendritic cells are mainly found in the paracortex.

    Spleen

    • The spleen is a large encapsulated organ found in almost all vertebrate animals.
    • It is structured by a network of connective tissue trabeculae.
    • The spleen filters blood for blood-borne antigens, cellular debris, and aged blood cells.
    • It stores red blood cells, platelets, and recycles iron.

    Peyer's Patches

    • Peyer's patches are non-encapsulated lymphoid tissue located in the wall of the small intestine.
    • In ruminants, pigs, dogs, and rabbits, they are found in the ileum and are primary lymphoid organs for B cell development.
    • They contain densely packed lymphoid follicles with only B lymphocytes.
    • They undergo involution.

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    Description

    Learn about the cells and organs that make up the immune system and delve into the fundamentals of immunology. This quiz provides insights into how organisms respond to antigen challenges, distinguish self from non-self, and explore the various aspects of immune phenomena.

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