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Questions and Answers

What is the main function of the lymphatic system?

  • To produce hormones
  • To defend the body against environmental hazards and internal threats (correct)
  • To regulate body temperature
  • To transport oxygen and carbon dioxide throughout the body

    • The lymphatic system is made up of only lymphoid organs.

    False (B)

    What is the fluid called that is similar to plasma but lacks plasma proteins?

    Lymph

    Which of these is NOT a component of the lymphatic system?

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

    What is the role of the thymus in the lymphatic system?

    <p>Maturing T lymphocytes (C)</p> Signup and view all the answers

    What is the term for the ability to resist infection and disease?

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

    Which type of immunity is present at birth?

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

    Adaptive immunity involves the production of antibodies by B cells.

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

    Match the following types of lymphocytes with their functions:

    <p>Cytotoxic T cells = Destroy infected or abnormal cells using perforins and lymphotoxins Helper T cells = Stimulate the adaptive immune response by activating B cells and cytotoxic T cells Regulatory T cells = Maintain immune homeostasis by suppressing immune responses, preventing autoimmune reactions Memory T cells = Respond quickly to previously encountered antigens, providing long-lasting immunity</p> Signup and view all the answers

    What type of cells are responsible for immune surveillance?

    <p>Natural killer (NK) cells</p> Signup and view all the answers

    Interferons are chemical messengers that can inhibit viral replication.

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

    Which of the following is NOT a function of the complement system?

    <p>Regulating body temperature (A)</p> Signup and view all the answers

    What are the four hallmark signs of inflammation?

    <p>Redness, swelling, heat, and pain</p> Signup and view all the answers

    Which of the following is a function of fever?

    <p>Inhibiting some viruses and bacteria (C)</p> Signup and view all the answers

    Adaptive immunity is also known as specific immunity.

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

    What do plasma cells produce?

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

    Helper T cells suppress the activity of B cells.

    <p>False (B)</p> Signup and view all the answers

    What is the name for the major histocompatibility complex found in chromosome 6?

    <p>MHC (Major Histocompatibility Complex)</p> Signup and view all the answers

    What is the primary role of MHC I proteins?

    <p>Presenting antigens to cytotoxic T cells (B)</p> Signup and view all the answers

    Antigen recognition occurs when an antigen matches the specific receptor on a T cell.

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

    What is the name of the protein complex found on all T cells that plays a role in antigen recognition?

    <p>CD3 receptor complex</p> Signup and view all the answers

    CD8 markers are primarily found on which type of T cells?

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

    Costimulation is the second signal required for complete T cell activation.

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

    What is the primary function of cytotoxic T cells?

    <p>Destroying infected or abnormal cells (A)</p> Signup and view all the answers

    What is the name for inactive lymphocytes that remain in circulation after an infection, providing long-lasting immunity?

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

    Regulatory T cells are responsible for suppressing B cell activity.

    <p>False (B)</p> Signup and view all the answers

    Helper T cells produce cytokines that can stimulate cytotoxic T cell activity.

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

    What is the name for chemical messengers released by cells involved in the immune response?

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

    Which of the following is NOT a group of cytokines?

    <p>Growth hormones (B)</p> Signup and view all the answers

    Interleukins can enhance innate immunity by stimulating mast cell formation and inflammation.

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

    What is the primary function of interferons?

    <p>Making cells resistant to viral infection (C)</p> Signup and view all the answers

    What is the name for factors produced by active T cells, macrophages, and other cells that stimulate the production of blood cells in the bone marrow?

    <p>Colony-stimulating factors (CSFs)</p> Signup and view all the answers

    B cell sensitization occurs when an antigen binds to a B cell receptor.

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

    What is the function of plasma cells?

    <p>Secrete antibodies (D)</p> Signup and view all the answers

    Antibodies are composed of two pairs of polypeptide chains: heavy chains and light chains.

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

    What is the term for specific sites on an antigen that antibodies bind to?

    <p>Antigenic determinant sites (epitopes)</p> Signup and view all the answers

    IgG is the largest and most diverse class of antibodies, accounting for about 80% of all antibodies in the body.

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

    Which class of antibodies is primarily responsible for allergic reactions?

    <p>IgE (B)</p> Signup and view all the answers

    What is the term for the level of antibodies in plasma?

    <p>Antibody titer</p> Signup and view all the answers

    The secondary immune response is typically slower and weaker than the primary immune response.

    <p>False (B)</p> Signup and view all the answers

    What is the term for the ability to produce an immune response after exposure to an antigen?

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

    Which of these factors can negatively impact the immune response?

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

    Autoimmune disorders occur when the immune system mistakenly attacks the body's own tissues.

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

    Which of the following is NOT an example of an autoimmune disorder?

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

    What is term for the type of immunity that is acquired through vaccines?

    <p>Artificially acquired active immunity</p> Signup and view all the answers

    Immunodeficiency diseases can be caused by problems with embryonic development, viral infections, or immunosuppressive drugs.

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

    Which of the following is NOT a defense mechanism against bacterial infection?

    <p>Inhibition of viral replication (A)</p> Signup and view all the answers

    The immune response to viral infections primarily involves the activation of cytotoxic T cells and the production of antibodies.

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

    What term describes the excessive immune response to allergens?

    <p>Hypersensitivity (allergies)</p> Signup and view all the answers

    Anaphylaxis is a life-threatening systemic allergic reaction.

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

    What is the primary action of antihistamines?

    <p>Blocking the action of histamine (C)</p> Signup and view all the answers

    The immune system becomes less efficient with age, increasing the risk of infections and cancer.

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

    Study Notes

    Prayer Before Class

    • Holy Spirit, true source of light and wisdom
    • Pour forth brilliance upon dense intellect
    • Dissipate darkness of sin and ignorance
    • Grant a penetrating mind to understand
    • A retentive memory, method and ease of learning
    • Lucidity to comprehend
    • Abundant grace in expressing oneself
    • Guide the beginning, direct its progress, and bring work to successful completion
    • This is asked through Jesus Christ
    • Living and reigning with the Father, forever and ever, Amen .

    Fundamentals of Anatomy & Physiology

    • Chapter 22: The Lymphatic System and Immunity
    • Lecture Presentation by Dr. Virginia Irintcheva, Truckee Meadows Community College

    Introduction

    • Lymphatic system (lymphoid system): cells, tissues, and organs responsible for defending the body from environmental hazards and internal threats
    • Immune system: all body cells and tissues involved in immunity, including parts of the lymphatic, integumentary, skeletal, cardiovascular, respiratory, and digestive systems
    • Immunity: the ability to resist infection and disease
    • Pathogens: organisms that cause disease (viruses, bacteria, fungi, and parasites)

    Components of the Lymphatic System

    • Lymph: fluid similar to plasma but without plasma proteins
    • Lymphatic vessels: carry lymph from peripheral tissues to veins
    • Lymphoid cells: lymphocytes, phagocytes, and other cells
    • Lymphoid tissues: connective tissues dominated by lymphocytes
    • Lymphoid organs: organs where lymphocytes may form, mature, or become activated

    The Components of the Lymphatic System (diagram)

    • Lymph Nodes and Lymphatic Vessels (diagram)
    • Meningeal lymphatics
    • Cervical lymph nodes
    • Thoracic duct
    • Right lymphatic duct
    • Axillary lymph nodes
    • Lymphatics of mammary gland
    • Cisterna chyli
    • Lymphatics of upper limb
    • Lumbar lymph nodes
    • Other Lymphoid Tissues and Organs: Tonsil, Thymus, Spleen, Mucosa-associated lymphatic tissue(MALT) in digestive, respiratory, urinary, and reproductive tracts

    The Components of the Lymphatic System (diagram 2)

    • Includes:
    • Pelvic lymph nodes
    • Inguinal lymph nodes
    • Lymphatics of lower limb
    • Appendix
    • Red bone marrow

    Primary and Secondary Lymphoid Tissues and Organs

    • Primary lymphoid tissues and organs: sites where lymphocytes are formed and mature.
    • Red bone marrow and thymus
    • Secondary lymphoid tissues and organs: sites where lymphocytes are activated for different types of immunity.
    • Tonsils, mucosa associated lymphatic tissue (MALT), lymph nodes, and spleen

    Functions of the Lymphatic System

    • Produce, maintain, and distribute lymphocytes and other lymphoid cells
    • Return excess fluid from tissues to the bloodstream to maintain normal blood volume
    • Regulate the composition of interstitial fluid by transporting hormones, nutrients, and wastes from their tissues of origin to the general circulation

    Lymphatic Vessels and Lymphatic Capillaries

    • Lymphatic vessels (lymphatics): carry lymph from peripheral tissues to the venous system
    • Lymph: interstitial fluid that has entered the lymphatic vessels
    • Meningeal lymphatics: network of vessels in the dura mater that drains cerebrospinal fluid (CSF) to cervical lymph nodes, remove wastes and transport immune cells
    • Lymphatic capillaries: smallest lymphatic vessels, found in almost every tissue of the body
    • Lymphatic lacteals: lymphatic capillaries in the small intestine that transport lipids absorbed by the digestive tract

    Lymphatic Capillaries (details)

    • Compared to blood capillaries, lymphatic capillaries are closed at one end, begin in tissues, have larger luminal diameters, thinner walls, and a flattened or irregular outline in sectional view.
    • Endothelial cells loosely bound together, overlap of endothelial cells acts as a one-way valve
    • Allow fluids, solutes, viruses, and bacteria to enter and prevents them from returning to the intercellular spaces

    Lymph Flow and Lymph Nodes

    • Lymph flows from lymphatic capillaries to larger lymphatic vessels
    • Small to medium lymphatic vessels contain three layers in the vessel wall similar to veins; contain valves to prevent lymph backflow, and often share the same path with blood vessels
    • Lymphedema: obstruction of lymphatic vessels that prevents lymph drainage, causes severe swelling which can become permanent, interferes with immune system function

    Major Lymph-Collecting Vessels

    • Superficial lymphatics: vessels in the subcutaneous layer, areolar layer of mucous membranes and serous membranes
    • Deep lymphatics: larger vessels that accompany arteries and veins
    • Superficial and deep lymphatics converge to form large lymphatic trunks that empty into two major collecting vessels:
    • Thoracic duct
    • Right lymphatic duct

    Thoracic Duct and Right Lymphatic Duct

    • Thoracic duct: collects lymph from all body regions inferior to the diaphragm and from the left side of the body superior to the diaphragm
    • Cisterna chyli: expanded chamber at the base of the thoracic duct
    • Receives lymph from the inferior parts of the abdomen, pelvis and lower limbs
    • The thoracic duct empties into the left subclavian vein
    • Right lymphatic duct: collects lymph from the right side of the body superior to the diaphragm, empties into the right subclavian vein

    Lymphoid Cells (Details)

    • Lymphoid cells: immune system cells and support cells in lymphoid tissues
    • Phagocytic immune system cells: macrophages, microphages, and other phagocytes
    • Lymphocytes: immune system cells that respond to specific invading pathogens
      • T cells (thymus-dependent)
      • B cells (bone marrow-derived)
      • N K cells (natural killer)

    Lymphoid Tissues (Details)

    • Lymphoid nodules (lymphatic nodules): areolar tissue densely packed with lymphocytes
    • Lymphoid nodules in the deep to the respiratory mucosa = tonsils
    • Present along the digestive, urinary, and reproductive tracts, distributed in lymphatic organs such as lymph nodes and spleen
    • Germinal center: central zone of the nodule that contains dividing lymphocytes

    Lymphoid Tissues (Tonsils)

    • Tonsils: large lymphoid nodules in the wall of the pharynx
      • Pharyngeal tonsil (adenoids): posterior wall of the nasopharynx
      • Left and right palatine tonsils: posterior inferior margin of the oral cavity
      • Two lingual tonsils: deep to the epithelium covering the base of the tongue
    • Tonsillitis: inflammation of the tonsils, especially palatine tonsils

    Lymphoid Tissues (MALT)

    • Mucosa-associated lymphoid tissue (MALT): lymphoid tissues associated with the mucosa of the digestive, respiratory, urinary, and reproductive systems
    • Aggregated lymphoid nodules (Peyer's patches): clusters of lymphoid nodules deep to intestinal epithelial lining
    • Appendix (vermiform appendix): tube-shaped sac between the small and the large intestine
      • Contains a mass of fused lymphoid nodules

    Lymphoid Organs

    • Lymphoid organs: separated from the surrounding tissues by a connective tissue capsule
    • Lymph nodes
    • Thymus
    • Spleen

    Lymph Nodes (Structure)

    • Lymph nodes: small lymphoid organs found along lymphatic vessels
      • Structure: surrounded by a capsule, trabeculae, hilum, afferent lymphatics (carry lymph from peripheral tissues to the node), efferent lymphatics (carry lymph away)

    Lymph Nodes (Functions)

    • Lymph node functions: filters lymph before it returns to the venous circulation, removes 99 percent of antigens (foreign microorganisms and substances), phagocytes engulf debris and pathogens in the lymph node or arrive at the lymph node from peripheral tissues, Antigens are then presented to lymphocytes; lymphoid tissues and lymph nodes monitor peripheral infections and activate the immune response before they reach vital organs

    Lymph Nodes (additional info)

    • Lymph nodes of the gut, trachea, lungs and the thoracic duct protect against pathogens in the digestive and respiratory systems, Largest lymph nodes found in the groin, axillae, and base of neck, Activated lymph nodes enlarge due to cell division of lymphocytes and phagocytes, Lymphadenitis - inflammation of the lymph nodes, Lymphadenopathy - disease/excessive enlargement of lymph nodes

    Thymus

    • Thymus: pink, grainy lymphoid organ located in the mediastinum above the heart
    • Atrophy after puberty, Inactive afterward
    • Structure: Divided into two thymic lobes, Divided into smaller lobules by septa
      • Outer cortex: contains densely packed lymphocytes surrounded by epithelial reticular cells
      • Inner medulla: contains epithelial reticular cells in concentric layers (Hassall's corpuscles)

    Thymus (Functions)

    • Regulates T cell lymphocyte development and maturation
    • T cells divide in the cortex, maturing T cells migrate into the medulla, mature T cells leave via medullary blood vessels
    • Epithelial reticular cells maintain the blood thymus barrier (to separate developing T cells from the general circulation)
    • Hormone production: Thymosin (an extract from thymus containing several hormones that promote T cell development and maturation)

    Spleen

    • Spleen: large lymphoid organ lateral to the stomach
    • Functions: Filters blood to remove abnormal blood cells and other blood components by phagocytosis, storage of iron recycled from red blood cells, immune responses to antigens in blood by macrophages, B cells, and T cells

    Spleen (additional details)

    • Spleen Attached to the stomach by the gastrosplenic ligament, Contacts the diaphragm and the left kidney, Splenic veins, arteries, and lymphatic vessels enter the spleen at the hilum; Cellular components within the capsule make up the pulp (Red pulp contains many red blood cells, White pulp resembles lymphoid nodules)

    Innate and Adaptive Immunity

    • Immunity: the ability to resist and defend against infectious organisms and other damaging substances
    • Immune response: body's reaction to infectious agents and other abnormal substances
    • Resistance: ability of the body to maintain immunity
    • Types of Immunity:
      • Innate (nonspecific): physical barriers, phagocytes, immune surveillance, interferons, complement, inflammation, fever. Present at birth, and always works the same way against any type of threat.
      • Adaptive (specific): protects against specific antigens, depends on activities of B and T lymphocytes, develops when there is exposure to an antigen, and protects against future attacks by the same pathogen.

    Lymphocytes

    • Lymphocytes - B cells, T cells, and N K cells
    • Lymphocyte distribution: tissues maintain different T cell and B cell populations, lymphocytes move through tissues and enter blood vessels or lymphatics for transport. Have a long life-span
    • Lymphocytopoiesis: involves the red bone marrow, thymus, and peripheral lymphoid tissues; hemocytoblasts in the bone marrow divide lymphoid stem cells which produce all lymphocytes.

    Lymphoid Stem Cells

    • One group of stem cells remains in the bone marrow and develops with the help of stromal cells to produce B cells and N K cells
    • B cells differentiate with exposure to interleukin-7
    • As they mature, B cells and N K cells enter the circulation and migrate to peripheral tissues
    • A second population migrates to the thymus (develop and mature in an environment isolated from blood). T cells differentiate and are selected with exposure to hormones. When they mature they enter the circulation and travel to peripheral tissues.

    Innate Defenses (Details)

    • Physical barriers
    • Phagocytes: neutrophils and eosinophils enter peripheral tissues to fight infections by phagocytosis, macrophages are large phagocytic cells derived from monocytes make up the monocyte-macrophage system (reticuloendothelial system)
      • Fixed macrophages reside in specific tissues and organs; Microglia found in the central nervous system, Stellate macrophages (Kupffer cells) found in liver sinusoids
      • Free macrophages travel throughout the body, migrate to tissues, alveolar macrophages (dust cells) found in the lungs
    • Immune surveillance
    • Interferons
    • Complement
    • Inflammation
    • Fever
    • Immune surveillance: destruction of abnormal cells by NK cells in peripheral tissues
    • Interferons: chemical messengers (coordinate the body's defenses against viral infections
    • Complement: system of circulating proteins that assist antibodies in the destruction of pathogens, lyses of cells, and enhances phagocytosis and inflammation. There are three pathways: Classical, Lectin, Alternative pathways

    Types of Vaccines

    • Inactivated vaccines: contain killed pathogens.
    • Live-attenuated vaccines: use live, weakened forms of a pathogen.
    • Messenger RNA (mRNA) vaccines: stimulate synthesis of viral proteins that trigger an immune response.
    • Subunit, recombinant, polysaccharide, and conjugate vaccines: use pieces of the pathogen.
    • Toxoid vaccines: use altered or weakened forms of bacterial toxins.
    • Viral vector vaccines: use modified versions of a different virus to deliver protection.

    Properties of Adaptive Immunity

    • Specificity
    • Versatility
    • Memory
    • Tolerance

    T Cells and Immunity (Antigen Presentation)

    • T cells recognize antigens that are "presented" by antigen-presenting cells.
    • MH C proteins: membrane glycoproteins that serve as "signature" to identify the cell as "self."
    • Genetically coded by the major histocompatibility complex (MHC) in chromosome 6 (Also called human leukocyte antigens (HLA))
    • Antigen presentation occurs when an antigen-MHC protein combination appears in the membrane and is recognized by a T cell.

    Antigen Presentation (MHC Classes)

    • Classes of MHC proteins
      • Class I MHC proteins: found in membranes of all nucleated cells, pick up small peptides from the cytoplasm, and present them on the cell surface; T cells ignore peptides from normal healthy cells, abnormal peptides or viral proteins activate T cells
      • Class II MHC proteins: found in membranes of lymphocytes and antigen-presenting cells (APCs)
      • Antigen processing: APCs engulf and break down pathogen antigens and antigenic fragments, bind to class II MHC proteins and are presented on the plasma membrane. T cells recognize and get activated.

    B Cells and B Cell Sensitization

    • B cell sensitization: B cells have specific surface antibodies (B cell receptors)
    • Antigen in interstitial fluids binds to a corresponding B cell receptor, the antigen is taken into the B cell by endocytosis and processed
    • Reappears on the surface, bound to a MHC protein (Class II)

    B Cell Activation 

    • Sensitized B cell present the antigen via Class II MHC to a helper T cell
    • The helper T cell secretes cytokines that promote B cell activation.
    • The activated B cell undergoes cell division.
    • Some daughter cells differentiate into plasma cells and synthesize and secrete antibodies into interstitial fluid.
    • Memory B cells remain in reserve in the circulation to respond to the next infection.

    Antibodies (Structure)

    • Antibodies: soluble proteins
    • Structure: Two pairs of polypeptide chains (one pair of heavy chains, one pair of light chains), each chain has  constant and variable segments, variable segments form antigen-binding sites  that bind to antigenic determinants (epitopes) of antigen molecules

    Antibody Structure and Function (Diagram)

    • Antigen-binding site
    •   Heavy chain
    •   Disulfide bond
    • Light chain
    • Complement binding site
    • Site of binding to macrophages

    Classes of Antibodies (Immunoglobulins)

    • Classes of antibodies/Immunoglobulins: Ig G, Ig D, Ig M, Ig A, Ig E

    IgG

    • Largest and most diverse class of antibodies.
    • 80 percent of all antibodies
    • Responsible for resistance against many viruses, bacteria, and bacterial toxins
    • Can cross the placenta. Maternal Ig G provides passive immunity to the fetus. Anti-Rh antibodies produced by Rh-negative mothers that produce hemolytic disease of newborn are IgG.

    IgE

    • Attaches to the exposed surfaces of basophils and mast cells
    • When an antigen is bound by an IgE molecule, these cells are stimulated to release histamine and other chemicals that accelerate inflammation. Also important in the allergic response.

    IgD 

    • Antibodies on the surface of B cells.
    • Binding plays a role in sensitization of the B cell.

    IgM

    • First class of antibody secreted.
    • Concentration declines as production accelerates.
    • Plasma cells secrete individual IgM molecules that polymerize and circulate as five-antibody units
    • Anti-A and anti-B antibodies responsible for agglutination of incompatible blood types
    • May also attack bacteria that are insensitive to IgG.

    IgA

    • Found in glandular secretions such as mucus, tears, saliva and semen.
    • Attacks pathogens before they gain access to internal tissues.
    • Circulates in the blood in either individual or in pairs.
    • Epithelial cells absorb antibodies from the blood before releasing IgA into the epithelial surface. 

    Antigen-Antibody Complex

    • Antigen-antibody complex: antibody bound to an antigen.
    • A complete antigen has at least two antigenic determinant sites.
    • Binds to both antigen-binding sites of the variable segments of an antibody.
    • Exposure to a complete antigen leads to B cell sensitization and immune response.
    • Hapten: partial antigen. Must attach to a carrier molecule to act as complete antigen. Antibodies will attack both the hapten and the carrier molecule. If carrier is normal, the antibody attacks normal cells (example: penicillin allergy)

    Antibody Structure and Function (diagram of complete antigen/hapten)

    • Complete antigen
    • Hapten
    • Carrier molecule

    Actions of Antibodies

    • Neutralization: prevents pathogens or toxins from binding and entering cells.
    • Precipitation and agglutination: formation of immune complexes that precipitate out of solution.
    • Complement activation: complement proteins destroy the antigen.
    • Attraction of phagocytes: phagocytize and destroy the antigen-antibody complexes
    • Opsonization (coating): increase phagocyte efficiency.
    • Stimulation of inflammation: stimulate mast cells and basophils
    • Prevention of bacterial and viral adhesion: preventing pathogens from entering the body

    Immune Responses to Antigen Exposure

    • Primary response: occurs after initial exposure to an antigen. Takes time to develop. Antibody titer (level of  antibodies in the plasma) rises slowly; peak response takes  2 weeks then declines rapidly. IgM antibodies are produced first.
    • Secondary response: a subsequent exposure to the same antigen. Activates memory B cells at low concentrations. Antibodies are secreted in massive quantities immediately. IgG antibodies rise very high and very quickly. IgM production is quicker.

    Immunocompetence

    • Immunocompetence: ability to produce an immune response after exposure.
    • Development:
      • Cell-mediated immunity begins as early as the 3rd month of fetal development and antibody-mediated by the 4th month.
      • ACPs take residence in different tissues. Fetus receives IgG antibodies from the mother across the placenta and after birth, the infant receives IgA antibodies from the milk.
    • Immunocompetence continues during childhood; with continual exposure to antigens, circulating antibodies and memory B and T cells increase.

    Cells that Participate in Tissue Defenses

    • Neutrophils
    • Eosinophils
    • Mast cells and basophils
    • Macrophages (free and fixed, stellate macrophages, and microglia)
    • Dendritic cells
    • NK cells
    • Cytotoxic T cells (CD8 marker) 

    Cells that Participate in Tissue Defenses (additional cells)

    • Helper T cells (CD4 marker)
    • B cells
    • Regulatory T cells (CD8 marker)
    • Memory cells (T cells and B cells)

    Immune Response to Bacterial Infection

    • In the early stages of infection, neutrophils and NK cells migrate to the area and destroy bacteria
    • Cytokines draw more phagocytes to the area.
    • Cytotoxic T cells are activated by antigen presentation and destroy the bacteria
    • B cells are activated and antibody concentration rises. Antibodies bind to bacteria, their toxins and target them for destruction by lysis or phagocytosis.

    Immune Response to Viral Infection

    • Infected tissue cells release interferons to limit viral spread.
    • Infected cells also present the virus on their plasma membranes to activate NK and cytotoxic T cells to destroy the infected cells.
    • APCs also present the virus and activate helper T cells
    • B cells become activated and produce antibodies that target the virus for destruction and prevent it from entering cells.

    Stress and the Immune Response

    • Interleukin-1 stimulates the release of ACTH which stimulates the adrenal cortex to produce glucocorticoids, secreted to limit the immune response.
    • Long-term secretion (chronic stress) inhibits the immune response and lowers resistance to disease
    • Functions of glucocorticoids: Depression of inflammation, reduction in the abundance and activity of phagocytes in peripheral tissues; inhibition of interleukin secretion depresses the response of lymphocytes.

    Immune Disorders: Hypersensitivities

    • Hypersensitivities (allergies) - excessive immune responses to antigens
    • Allergens: antigens that trigger allergic reactions
      • Categories of hypersensitivities
        • Immediate hypersensitivity (Type I)
        • Cytotoxic reactions (Type II)
        • Immune complex disorders (Type III)
        • Delayed hypersensitivity (Type IV)

    Immediate Hypersensitivity

    • Rapid and especially severe response to an antigen. Examples: environmental allergies
    • Sensitization to an allergen leads to the production of large amounts of IgE antibodies that bind to basophils and mast cells.
    • Subrequent encounter causes the antibodies to bind to basophils and mast cells, and the cells release histamine, heparin, cytokines, and prostaglandins, which cause sudden massive inflammation
    • Severity of the reaction depends on individual sensitivity and locations involved. Allergens in the bloodstream may cause anaphylaxis.

    Immediate Hypersensitivity (Anaphylaxis)

    • Anaphylaxis - systemic allergic reaction. Can be fatal
    • Changes capillary permeability, produces swelling and hives on skin. Smooth muscles of respiratory system contract, making breathing difficult. Widespread peripheral vasodilation can cause circulatory collapse (anaphylactic shock).

    Antihistamines

    • Antihistamines: drugs that block the action of histamine, can relieve mild symptoms of immediate hypersensitivity. Example: Benadryl.

    Autoimmune Disorders

    • Autoimmune disorders - the immune system malfunctions to attack “self” antigens.
    • Sometimes the self-antigens are similar to foreign antigens and the immune system is confused.
    • Activated B cells make autoantibodies against body cells.
    • Examples: Thyroiditis, Rheumatoid arthritis, Type 1 diabetes, and Multiple sclerosis.

    Immunodeficiency Diseases

    • Immunodeficiency diseases - result from problems with embryonic development of lymphoid organs and tissues.
    • Viral infections, immunosuppessive drugs, and radiation treatments can cause immunodeficiency.
    • Severe combined immunodeficiency disease (SCID) - genetic disease. Leads to absence of cell-mediated or antibody-mediated immunity.
    • Infection with Human Immunodeficiency Virus (HIV) destroys helper T cells and can result in AIDS (acquired immunodeficiency syndrome).

    Effects of Aging on Immune Response

    • The immune response diminishes with age, increasing vulnerability to infections and cancer.
    • Effects of aging: Thymic hormone production is greatly reduced; T cells become less responsive to antigens; fewer helper T cells reduces responsiveness of B cells; immune surveillance against tumor cells declines.

    Immune System Integration

    • The nervous and endocrine systems can influence the immune response.

    Prayer After Class

    • Grant wisdom to know God, a seeking heart, and conduct pleasing to God. Faithful perseverance in waiting and a hope of finally embracing God. Amen.

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