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Chapter 14: Lymphatic and Immune Systems

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Title: Chapter 14: Lymphatic and Immune Systems


1
Chapter 14 Lymphatic and Immune Systems
2
The Lymphatic System
  • The lymphatic system has three main functions
  • lymphatic vessels return excess tissue fluid to
    the bloodstream,
  • lacteals in the small intestine receive and
    transport lipoproteins, and
  • lymphoid organs work with the immune system to
    combat disease.

3
Lymphatic Vessels
  • The lymphatic vessels are similar in structure
    and function to veins movement of lymph is
    dependent upon skeletal muscle contraction, and
    internal valves prevent backflow.
  • Lacteals collect fat molecules at intestinal
    villi and lymphatic capillaries collect excess
    tissue fluid at blood capillaries.

4
  • Tissue fluid becomes lymph once it enters the
    lymphatic capillaries.
  • Lymphatic capillaries merge to form larger
    lymphatic vessels that carry lymph to the
    subclavian veins.
  • Edema is retention of fluids in the tissues due
    to a blockage of the flow of lymph.

5
Lymphatic system
6
Lymphoid Organs
  • Lymphoid organs include the lymph nodes, tonsils,
    spleen, thymus gland, and the red bone marrow.
  • Lymph nodes are located at certain points along
    lymphatic vessels and contain a cortex and a
    medulla.
  • The cortex contains nodules where lymphocytes
    congregate when fighting off a pathogen.

7
  • Macrophages are concentrated in the medulla where
    they work to cleanse the lymph.
  • Tonsils are patches of lymphatic tissue in the
    pharynx they are the first to encounter
    pathogens in the nose and mouth.
  • Tonsils perform functions similar to those of the
    lymph nodes.
  • The spleen cleanses blood of pathogens and their
    toxins.

8
  • The thymus is located behind the sternum and is
    the site in which T lymphocytes mature.
  • The thymus produces the hormone thymosin that
    appears to cause T lymphocytes to mature
    thymosin may play other roles in immunity.
  • The red bone marrow is the site where all types
    of blood cells are produced by stem cells.
  • B lymphocytes mature in the red bone marrow.

9
The lymphoid organs
10
Nonspecific Defenses
  • The immune system includes cells and tissues that
    are responsible for immunity.
  • Immunity is the bodys ability to defend against
    infection and involves nonspecific and specific
    defenses.
  • The nonspecific defenses are effective against
    many types of infectious agents.

11
Barriers to Entry
  • Skin and mucous membranes lining the respiratory,
    digestive and urinary tracts, oil glands in the
    skin, ciliated cells that sweep particles in
    mucus, and an acidic stomach all contribute to
    keeping pathogens from entering the body.
  • Beneficial bacteria in the intestines and vagina
    also prevent pathogens from taking up residence.

12
Inflammatory Reaction
  • The inflammatory reaction involves redness, heat,
    swelling, and pain.
  • The release of histamine and kinins from damaged
    tissue cells and from mast cells causes redness
    and swelling.
  • The swollen area and kinins stimulate free nerve
    endings, causing the sensation of pain.

13
  • Macrophages migrate to the site of injury and can
    engulf pathogens and also release
    colony-stimulating factors that cause the bone
    marrow to release more white blood cells.
  • Anti-inflammatory drugs combat chronic
    inflammation by acting against chemical mediators
    released by white blood cells.
  • The presence of pus indicates the body is trying
    to overcome the infection.

14
Inflammatory reaction
15
Natural Killer Cells
  • Natural killer cells kill virus-infected cells
    and tumor cells by cell-to-cell contact.
  • They are large, granular lymphocytes with no
    specificity and no memory.
  • Their number is not increased by prior exposure
    to that kind of cell.

16
Protective Proteins
  • The complement system, or complement, refers to a
    number of plasma proteins that assist nonspecific
    immunity.
  • A small amount of activated complement protein is
    needed to activate a cascade of other proteins.
  • Complement is activated when pathogens enter the
    body.

17
  • Complement amplifies the inflammatory reaction by
    attracting phagocytes and promoting phagocytosis.
  • Some complement proteins join to form pores in
    the surface of bacteria and cause them to burst.
  • Interferon is a protein produced by
    virus-infected cells that prepares non-infected
    cells for attack and interferes with viral
    replication it is specific to species.

18
Action of the complement system against a
bacterium
19
Specific Defenses
  • An antigen is any foreign substance that
    stimulates the immune system to react to it.
  • The body does not consider its own proteins
    foreign therefore the immune system must
    distinguish self from nonself.
  • Lymphocytes have a large number of antigen
    receptors.

20
  • Specific defenses require B lymphocytes (B cells)
    and T lymphocytes (T cells), which are both
    produced in the bone marrow however, T cells
    mature in the thymus, while B cells mature in
    bone marrow.
  • B cells give rise to antibodies that are shaped
    like antigen receptors and are capable of
    combining with and neutralizing antigens.
  • T cells do not produce antibodies but instead
    attack foreign antigens directly.

21
B Cells and Antibody-Mediated Immunity
  • A toxin is a chemical produced by certain
    bacteria that is poisonous.
  • As a B cell encounters a bacterial cell or a
    toxin with a specific antigen in a lymph node or
    spleen, it is activated to divide.
  • The resulting cells are plasma cells, mature B
    cells that mass-produce antibodies.
  • Defense by B cells is thus called
    antibody-mediated immunity.

22
  • According to the clonal selection theory, it is
    the antigen that selects which lymphocyte will
    undergo clonal expansion, mass producing
    lymphocytes bearing matching antigen receptors.
  • Some members of the clone become memory B cells
    that remain in the body to divide and produce
    more lymphocytes able to secrete antibodies if
    the same antigen is encountered at a later date.
  • When infection passes, plasma cells undergo
    apoptosis.

23
Clonal selection theory and B cells
24
Structure of IgG
  • The most common type of antibody, the IgG
    antibody, is a Y-shaped molecule that has two
    binding sites for a specific antigen.
  • Antigen-antibody complexes often mark the antigen
    for destruction by neutrophils or macrophages, or
    they may activate complement.

25
Structure of IgG
26
Other Types of Antibodies
  • There are five types of antibodies
  • IgG the main type in circulation, binds to
    pathogens, activates complement, and enhances
    phagocytosis
  • IgM the largest type in circulation, activates
    complement and clumps cells
  • IgA found in saliva and milk, prevents
    pathogens from attaching to epithelial cells in
    digestive and respiratory tracts

27
  • IgD on surface of immature B cells, its
    presence signifies the readiness of a B cell
  • IgE found as antigen receptor on basophils in
    blood and on mast cells in tissues, responsible
    for immediate allergic response and protection
    against certain parasitic worms.
  • The different classes of antibodies vary in
    structure.

28
T Cells and Cell-Mediated Immunity
  • T cells mature in the thymus.
  • Like B cells, each T cell bears a specific
    receptor, however, for a T cell to recognize an
    antigen, the antigen must be presented by an
    antigen-presenting cell (APC).
  • When a viral or cancer cell antigen is presented,
    the antigen is first linked to a major
    histocompatibility complex (MHC) protein.

29
  • Human MHC proteins are called HLA (human
    lymphocyte-associated) antigens HLA antigens are
    self proteins that identify tissues as belonging
    to the body (the basis of tissue transplant
    rejection).
  • Once a T cells antigen receptor matches up to
    its specific antigen presented to it by a
    macrophage (the APC), the T cell becomes
    activated and secretes cytokines and undergoes
    clonal expansion.

30
Clonal selection theory and T cells
31
Types of T Cells
  • Cytotoxic T cells kill infected cells that bear a
    foreign antigen on contact using perforin
    molecules cytotoxic T cells provide
    cell-mediated immunity.
  • Helper T cells stimulate other immune cells and
    produce cytokines.
  • Some T cells are memory T cells that will
    jump-start an immune reaction upon re-infection.

32
Cell-mediated immunity
33
Induced Immunity
  • Immunity occurs naturally by infection or is
    induced by medical intervention.
  • The two types of induced immunity are active
    immunity and passive immunity.
  • In active immunity, the individual produces the
    antibodies against an antigen.
  • In passive immunity, the individual is given
    prepared antibodies.

34
Active Immunity
  • A person naturally develops active immunity after
    infection.
  • Immunization involves the use of vaccines,
    substances that contain an antigen to which the
    immune system responds.
  • Vaccines are available to induce long-lived
    active immunity in a well person.

35
  • After exposure to a vaccine, which is a
    non-virulent disease agent, antibodies are
    produced.
  • With a booster shot or second exposure, the
    antibody titer rises to a much higher level.
  • Active immunity is long-lived because there are
    memory B cells and memory T cells that will
    respond to lower doses of antigen in the body.

36
Active immunity due to immunizations
37
Passive Immunity
  • Passive immunity occurs when an individual is
    given prepared antibodies.
  • For example, a newborn has antibodies that passed
    from its mother through the placenta.
  • Breast-feeding passes antibodies from mother to
    child.
  • However, passive immunity is short-lived since
    the antibodies were not produced by the persons
    own B cells.

38
Passive immunity
39
Cytokines and Immunity
  • Cytokines are signaling molecules produced by T
    lymphocytes, monocytes, and other cells.
  • Both interferon and interleukins are cytokines
    used to improve a persons own T cell performance
    in fighting cancer.
  • Interleukins show promise in the treatment of
    chronic infectious diseases.

40
Monoclonal Antibodies
  • All plasma cells derived from the same B cell
    secrete an identical antibody.
  • B lymphocytes can therefore be exposed to a
    particular antigen and will produce monoclonal
    antibodies to the specific antigen.
  • Activated B lymphocytes are fused with myeloma
    cells and these hybridomas produce only one type
    of antibody.

41
Production of monoclonal antibodies
42
Immunity Side Effects
  • The immune system usually protects us from
    disease because it can distinguish self from
    nonself.
  • Sometimes, however, it responds in a manner that
    harms the body.
  • Examples include allergies, tissue-rejection
    reactions, or autoimmune diseases.

43
Allergies
  • Allergies are hypersensitivities to substances
    such as pollen or animal dander that are normally
    not harmful.
  • Weak antigens such as these are called allergens.
  • The response itself can cause some degree of
    tissue damage.

44
Immediate Allergic Response
  • An immediate allergic response can occur within
    seconds after contacting an antigen.
  • Anaphylactic shock is a severe reaction
    characterized by a sudden life-threatening drop
    in blood pressure.
  • Immediate allergic responses are caused by IgE
    antibodies attaching to mast cells and basophils
    these cells then release histamine which causes
    the symptoms of allergies, some of which are
    severe.

45
Delayed Allergic Response
  • Delayed allergic responses are started by memory
    T cells at the site of the allergen.
  • The response is regulated by cytokines secreted
    by T cells and macrophages.
  • Examples of delayed allergic responses include
    the skin test for tuberculosis and contact
    dermatitis from poison ivy, jewelry, and other
    possible irritants.

46
Blood-Type Reactions
  • Illness and death sometimes resulted from the
    first attempts at blood transfusions.
  • It was later discovered that only certain types
    of blood are compatible because red blood cell
    membranes carry proteins or sugar residues that
    are antigenic to recipients.
  • The ABO blood system represents a series of
    antigens on red blood cells that denote blood
    type.

47
ABO System
  • The ABO blood typing system is based on the
    presence of two antigens on the surface of red
    blood cells antigen A and antigen B.
  • Blood types include A, B, or AB, or type O, which
    has no antigens.
  • In the plasma there are two possible
    naturally-occurring antibodies anti-A and
    anti-B.

48
  • If the corresponding antigen and antibody are put
    together, clumping, or agglutination, occurs in
    this way the blood type of the individual may be
    determined.

49
Blood typing
50
Rh System
  • The Rh factor is also a blood type a person
    with this antigen on their red blood cells is Rh
    positive (Rh) those without it are Rh negative
    (Rh-).
  • Rh factor is important during pregnancy because
    an Rh- mother may form antibodies to the Rh
    antigen during the pregnancy or at the birth of a
    child who is Rh.

51
  • These antibodies can cross the placenta to
    destroy the red blood cells of any subsequent Rh
    child, causing hemolytic disease of the newborn.
  • A Rho-Gam injection uses anti-Rh antibodies to
    attack Rh cells before they can stimulate the
    mother to produce her own antibodies.

52
Hemolytic disease of the newborn
53
Tissue Rejection
  • Tissue rejection occurs when cytotoxic T cells
    bring about the destruction of foreign tissue in
    the body.
  • A close match between donor and recipient can
    reduce rejection.
  • Immunosuppressive drugs act by inhibiting the
    response of T cells to cytokines, but can result
    in kidney damage.

54
Autoimmune Diseases
  • Autoimmune disease occurs when cytotoxic T cells
    or antibodies mistakenly attack the bodys own
    cells as if they bear foreign antigens.
  • Autoimmune diseases include myasthenia gravis,
    multiple sclerosis, systemic lupus erythematosus,
    and rheumatoid arthritis.
  • It has been suggested that type I diabetes and
    heart damage after rheumatic fever are autoimmune
    diseases.

55
Chapter Summary
  • Lymphatic vessels form a one-way system that
    transports lymph from tissues and fat from
    lacteals to specific cardiovascular veins.
  • Lymphoid organs include the red bone marrow,
    spleen, thymus, and lymph nodes that all play
    critical roles in defense mechanisms.

56
  • Immunity consists of nonspecific and specific
    defenses to protect against disease.
  • Nonspecific defenses consist of barriers to
    entry, the inflammatory reaction, natural killer
    cells, and protective proteins.
  • Specific defenses involve two types of
    lymphocytes B lymphocytes and T lymphocytes.

57
  • Medically induced immunity involves use of
    vaccines to achieve long-lasting immunity and use
    of antibodies to provide temporary immunity.
  • While immunity protects us, it is also
    responsible for undesirable effects, such as
    allergies, autoimmune diseases, and tissue
    rejection.
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