The Lymphatic System and Body Defenses Chapter 12b

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The Lymphatic System and Body DefensesChapter
12b
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Fever

• Abnormally high body temperature
• Normal 36.2C 98.2F
• Hypothalmus heat regulation can be reset by
  pyrogens (secreted by white blood cells)
• High temperatures inhibit the release of iron and
  zinc from liver and spleen needed by bacteria

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• Destroy enzymes
• Fever also increases the speed of tissue repair

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Specific Defense The Immune System Third Line
of Defense

• 1st line- surface membrane barrier defensive
  cells
• 2nd line inflammatory response
• 3rd line
• Antigen specific recognizes and acts against
  particular foreign substances
• Systemic not restricted to the initial
  infection site
• Has memory recognizes and mounts a stronger
  attack on previously encountered pathogens

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Types of Immunity

• Humoral (fluid) immunity
• Antibody-mediated immunity
• Cells produce chemicals for defense
• Cellular immunity
• Cell-mediated immunity
• Cells target virus infected cells
• Lymphs directly lyse foreign cells or release
  chemicals that increase inflammatory response

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Antigens (Nonself)

• Any substance capable of exciting the immune
  system and provoking an immune response
• Examples of common antigens
• Foreign proteins
• Nucleic acids
• Large carbohydrates
• Some lipids
• Pollen grains
• Microorganisms

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Self-Antigens

• Human cells have many surface proteins
• Our immune cells do not attack our own proteins
• Our cells in another persons body can trigger an
  immune response because they are foreign
• Restricts donors for transplants

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Allergies

• Many small molecules (called haptens or
  incomplete antigens) are not antigenic, but link
  up with our own proteins
• The immune system may recognize and respond to a
  protein-hapten combination
• The immune response is harmful rather than
  protective because it attacks our own cells

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Common allergies

• Poison ivy
• Animal dander
• Detergents
• Hair dyes
• penicillin

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Cells of the Immune System

• Lymphocytes
• Originate from hemocytoblasts in the red bone
  marrow
• B lymphocytes become immunocompetent in the bone
  marrow produce antibodies
• T lymphocytes become immunocompetent in the
  thymus cell-mediated immunity
• Macrophages
• Arise from monocytes
• Become widely distributed in lymphoid organs
• Act as antigen presenters (foreign ags theyve
  eaten) to T lymphs

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Activation of Lymphocytes
Figure 12.11
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Humoral (Antibody-Mediated) Immune Response

• B lymphocytes with specific receptors bind to a
  specific antigen
• The binding event activates the lymphocyte to
  undergo clonal selection
• A large number of clones are produced (primary
  humoral response)

PRESS TO PLAY
HUMORAL IMMUNITY ANIMATION
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Humoral (Antibody Mediated) Immune Response

• Most B cells become plasma cells
• Produce antibodies to destroy antigens (2000
  abs/second)
• Activity lasts for four or five days, then plasma
  cell dies
• Ab level peaks at 10 days then declines
• Some B cells become long-lived memory cells
  (secondary humoral response)

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Humoral Immune Response
Figure 12.12
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Secondary Response

• Memory cells are long-lived
• A second exposure causes a rapid response
• The secondary response is stronger and longer
  lasting
• Ab peak at 2-3 days, remains high for weeks to
  months

Figure 12.13
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Active Immunity

• Your B cells encounter antigens and produce
  antibodies
• Active immunity can be naturally or artificially
  acquired
• Vaccines pneumonia, smallpox, polio, tetanus,
  etc.

Figure 12.14
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Passive Immunity

• Antibodies are obtained from someone else
• Conferred naturally from a mother to her fetus
• Conferred artificially from immune serum or gamma
  globulin used because disease would kill before
  active immunity develops
• Exposure to hepatitis
• Antivenom for snake bites
• Antitoxin for botulism, rabies tetanus
• Short lived

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• Immunological memory does not occur
• Protection provided by borrowed antibodies

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Monoclonal Antibodies

• Antibodies prepared for clinical testing or
  diagnostic services
• Cancer-fighting drugs
• Produced from descendents of a single cell line
• Examples of uses for monoclonal antibodies
• Diagnosis of pregnancy
• Treatment after exposure to hepatitis and rabies

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Antibodies (Immunoglobulins) (Igs)

• Soluble proteins secreted by B cells (plasma
  cells)
• Carried in blood plasma
• Capable of binding specifically to an antigen
• 5 classes IgG, IgA, IgD, IgE, IgM

Figure 12.15a
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Antibody Structure

• Four amino acid chains linked by disulfide bonds
• Two identical amino acid chains are linked to
  form a heavy chain 400 aa

Figure 12.15b
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Antibody Structure

• The other two identical chains are light chains
• Specific antigen-binding sites are present

Figure 12.15b
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Antibody Classes

• Antibodies of each class have slightly different
  roles
• Five major immunoglobulin classes
• IgM can fix complement
• IgA found mainly in mucus prevent pathogen
  from entering body
• IgD important in activation of B cell
• IgG can cross the placental barrier most
  abundant, can fix complement
• IgE involved in allergies

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• IgD, IgG, and IgE are Y shaped monomers
• IgA monomer dimer (2)
• IgM pentamers (5)

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Antibody Function

• Antibodies inactivate antigens in a number of
  ways
• Complement fixation causes lyses of cell
• Neutralization- abs bind bacterial exotoxins
  viruses to block harmful effects
• Agglutination- as in rbcs
• Precipitation- soluble ag complex precipitates
  out eaten by phagocytes

PRESS TO PLAY
ANTIBODY FUNCTION ANIMATION
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Antibody Function
Figure 12.16
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Cellular (Cell-Mediated) Immune Response

• Antigens must be presented by macrophages to an
  immunocompetent T cell (antigen presentation)
• T cells must recognize nonself and self (double
  recognition)
• After antigen binding, clones form as with B
  cells, but different classes of cells are produced

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Cellular (Cell-Mediated) Immune Response
Figure 12.17
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T Cell Clones

• Cytotoxic T cells
• Specialize in killing infected cells
• Insert a toxic chemical (perforin) into foreign
  cell membrane
• Helper T cells
• Recruit other cells to fight the invaders
• Interact directly with B cells
• Release lymphokines

PRESS TO PLAY
PRESS TO PLAY
CYTOTOXIC T CELLS ANIMATION
HELPER T CELLS ANIMATION
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T Cell Clones

• Suppressor T cells
• Release chemicals to suppress the activity of T
  and B cells
• Stop the immune response to prevent uncontrolled
  activity
• A few members of each clone are memory cells

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Summary of the Immune Response
Figure 12.19
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Organ Transplants and Rejection

• Major types of grafts
• Autografts tissue transplanted from one site to
  another on the same person
• Isografts tissue grafts from an identical
  person (identical twin)
• Allografts tissue taken from an unrelated
  person
• Xenografts tissue taken from a different animal
  species

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• Transplant recipients need to be on
  immunosuppressor drugs
• Suppresses their system against bacteria
  viruses too

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Organ Transplants and Rejection

• Autografts and isografts are ideal donors
• Xenografts are never successful
• Do use pig heart valves
• Allografts are more successful with a closer
  tissue match

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Disorders of Immunity Allergies
(Hypersensitivity)

• Abnormal, vigorous immune responses
• Types of allergies
• Immediate hypersensitivity
• Triggered by release of histamine from IgE
  binding to mast cells
• Reactions begin within seconds of contact with
  allergen blood vessels dilate leak runny
  nose, itching
• Anaphylactic shock dangerous, systemic response
• Allergen enters blood circulates throughout
  body, ex. Bee sting use epinephrine

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Disorders of Immunity Allergies
(Hypersensitivity)

• Types of allergies (continued)
• Delayed hypersensitivity
• Triggered by the release of lymphokines from
  activated helper T cells
• Symptoms usually appear 13 days after contact
  with antigen (ex. Poison ivy)
• Most are contact dermatitis
• Antihistamines dont work, use corticosteroids

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Allergy Mechanisms
Figure 12.20
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Disorders of Immunity Immunodeficiencies

• Production or function of immune cells or
  complement is abnormal
• May be congenital or acquired
• SCID- severe combined immunodeficiency
• ? B T cells, live in bubble, give bone marrow
  transplant
• Includes AIDS Acquired Immune Deficiency
  Syndrome
• ?T helper cells

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Disorders of Immunity Autoimmune Diseases

• The immune system does not distinguish between
  self and nonself
• The body produces antibodies and sensitized T
  lymphocytes that attack its own tissues
• 5 of adults, 2/3 are women

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Disorders of Immunity Autoimmune Diseases

• Examples of autoimmune diseases
• Multiple sclerosis white matter of brain and
  spinal cord are destroyed
• Myasthenia gravis impairs communication between
  nerves and skeletal muscles
• Juvenile diabetes destroys pancreatic beta
  cells that produce insulin
• Rheumatoid arthritis destroys joints

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Disorders of Immunity Autoimmune Diseases

• Examples of autoimmune diseases (continued)
• Graves disease - thyroid
• Systemic lupus erythematosus (SLE) affects
  kidney, heart, lung and skin
• Glomerulonephritis impairment of renal function

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Self Tolerance Breakdown

• Inefficient lymphocyte programming
• Self-reacting B or T lymphs are not eliminated,
  but escape into body
• Appearance of self-proteins in the circulation
  that have not been exposed to the immune system
• Eggs
• Sperm
• Eye lens

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Self Tolerance Breakdown

• Cross-reaction of antibodies produced against
  foreign antigens with self-antigens
• Rheumatic fever
• Streptococcus bacteria antibodies cross react
  with heart antigens, causing valve damage

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Developmental Aspects of the Lymphatic System and
Body Defenses

• Except for thymus and spleen, the lymphoid organs
  are poorly developed before birth
• Lymph vessels bud from veins
• See these nodes by 5th week of gestation
• A newborn has no functioning lymphocytes at
  birth only passive immunity from the mother

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• If lymphatics are removed or lost, severe edema
  results, but vessels grow back in time
• ex. mastectomy