Body Defenses

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Body Defenses

• Two Systems that DEFEND us
• NonSpecific Defense System
• Responds IMMEDIATELY to protect the body from ALL
  foreign substances
• Specific Defense System (Immune System)
• Attacks SPECIFIC foreign substances that enter
  the body. It protects us from bacteria, viruses,
  transplanted organs or grafts, and even our OWN
  cells that have turned against us.
• NON-SPECIFIC DEFENSES
• Definition Refers to the MECHANICAL Barriers
  that cover body surfaces and to CELLS and
  CHEMICALS that protect us from invading
  pathogens(harmful organisms)

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NON-SPECIFIC DEFENSES

• SURFACE MEMBRANE BARRIERS
• The bodys FIRST line of defense against the
  invasion of disease-causing organisms is the SKIN
  and MUCOUS MEMBRANES.
• The bodys SECOND line of defense against the
  invasion of disease-causing organisms are CELLS
  and CHEMICALS
• CELLS
• A. Phagocytes Engulf and destroy pathogens that
  break the Surface Membrane barriers
• B. Natural Killer(NK) cells Lyse and kill
  CANCER cells and virus infected body cells by
  attacking the target cells plasma membrane and
  releasing chemicals that cause the plasma
  membrane and nucleus to disintegrate.

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Non-Specific Body Defenses

• Inflammatory Response
• Triggered whenever body tissues are injured
• 4 Things that trigger the INFLAMMATORY RESPONSE
• Physical Trauma
• Intense Heat
• Irritating Chemicals
• Infections by viruses and bacteria
• 4 Cardinal Signs of INFLAMMATION
• Redness
• Heat
• Swelling
• Pain

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Non-Specific Body Defenses

• HOW does FEVER protect us?
• It is the bodys response to invading
  microorganisms(pathogens)
• Abnormally high body temperature is triggered by
  PYROGENS (chemicals secreted by WBCs and
  Macrophages that are exposed to foreign
  substances.
• It prevents the multiplication of bacteria and
  enhances body repair processes

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Specific Body Defenses

• The bodys THIRD line of defense is our IMMUNE
  SYSTEM
• IMMUNE RESPONSE Defn Antigen Specific defenses
  mounted by activated T Cells and B Cells
• THREE Important Aspects of the IMMUNE RESPONSE
• Antigen Specific It recognizes and acts against
  particular pathogens or foreign substances
• Systemic Immunity is NOT restricted to the
  initial infection site
• Memory - It recognizes and mounts even stronger
  attacks on previously encountered pathogens.
• TWO Separate Arms of our Immune System
• HUMORAL or Antibody-mediated Immunity
  Protection is provided by ANTIBODIES that are
  present in the bodys humors or fluids and are
  produced by B LYMPHOCYTES or B CELLS.
• CELLULAR or Cell-mediated Immunity Protection
  is provided by
• non-antibody producing LYMPHOCYTES called T
  CELLS that are living.

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Specific Body Defenses

• Q What Specific Cells does the Cell-Mediated Arm
  Target?
• A Virus Infected Tissue Cells, Cancer Cells,
  Cells of Foreign Grafts
• Q How do Lymphocytes act against these TARGET
  CELLS?
• A Either DIRECTLY by lysing the foreign cells,
  INDIRECTLY by releasing chemicals that enhance
  the Inflammatory Response OR activating other
  immune cells
• ANTIGEN Definition Any substance capable of
  triggering our Immune System to provoke an Immune
  Response.
• Most Antigens are LARGE complex molecules that
  arent normally present in our bodies. The
  STRONGEST antigens are PROTEINS.
• Q What is a HAPTEN or INCOMPLETE ANTIGEN?
• A A small molecule that links up with our own
  proteins. The immune system recognizes the combo
  as foreign and mounts an attack.
• Q Where are HAPTENS located?
• A Poison Ivy, Animal fur, detergents, hair
  dyes, cosmetics household products.
• Q What happens in a Penicillin Reaction?
• A Penicillin binds to our OWN blood
  proteins-Immune Systems attacks

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CELLS of the Immune System

• LYMPHOCYTES White Blood Cells
• Lymphocytes originate from hemocytoblasts in red
  bone marrow ends of long bones and flat bones.
• B LYMPHOCYTES (B Cells) produce antibodies and
  oversee HUMORAL IMMUNITY.
• T LYMPHOCYTES (T Cells) are NON-Antibody
  producing lymphocytes that oversee CELLULAR
  IMMUNITY.
• MACROPHAGES BIG EATERS/ Arise from monocytes
  formed in the Bone Marrow.
• Functions (2)
• Engulf foreign particles and PRESENT fragments of
  these antigens to T cells for destruction
  (antigen presenters)
• 2. Secrete a protein (called monokines) that
  activates T Cells.

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CELLS of the Immune System

• IMMUNOCOMPETENCE
• Defn The ability of the bodys immune cells to
  recognize SPECIFIC ANTIGENS that contain special
  receptors on their plasma membrane and to bind
  to them
• T-CELLS develop IMMUNOCOMPETENCE in the THYMUS
  gland.
• B-CELLS develop IMMUNOCOMPETENCE in the BONE
  MARROW.
• Once a Lymphocyte is Immunocompetent it will be
  able to react to ONE distinct Antigen ONLY,
  because all the Antigen receptors on its external
  surface are the SAME.
• GENETICS determines the SPECIFIC foreign
  substances our immune system will be able to
  recognize and resist.
• After becoming Immunocompetent, BOTH T CELLS B
  CELLS migrate to the following places where their
  encounters with antigens will occur
• Lymph Nodes 2. Spleen 3. Loose Connective Tissue
• MACROPHAGES remain fixed in the Lymphoid Organs.
• LYMPHOCYTES circulate continously through the
  body(especially T cells.)

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Humoral Immunity Antibodies

• The PRIMARY Immune Response in Humoral Immunity
  is called
• CLONAL SELECTION.
• Describe what happens in Clonal Selection
• B Cells and T Cells become sensitized through
  binding with an antigen. Lymphocytes multiply
  rapidly to form an army of cells EXACTLY like
  itself and bearing the same antigen specific
  receptors.
• Most B cell clones become PLASMA cells that
  produce ANTIBODIES.
• IMMUNOLOGICAL MEMORY
• Describe how Clones become MEMORY CELLS
• B cell clones that do not become plasma cells
  become long lived MEMORY CELLS capable of
  responding to the same antigens at later meetings
  with it.

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Active Passive Humoral Immunity

• ACTIVE IMMUNITY Immunity produced by an
  encounter with an antigen it DOES provide
  Immunological Memory
• HOW ACTIVE IMMUNITY IS ACQUIRED
• NATURALLY- Acquired during bacteria and viral
  infections. We may develop symptoms of the
  disease and suffer a little or a lot.
• ARTIFICIALLY Acquired when we receive VACCINES.
  Most Vaccines contain a dead or weakened
  pathogen.
• PASSIVE IMMUNITY Short Lived Immunity resulting
  from the introduction of borrowed antibodies
  obtained from an immune animal or human donor
  it DOES NOT provide Immunological Memory
• During Passive Immunity B Cells are NOT
  challenged by the antigen
• Immunological Memory does NOT occur during
  Passive Immunity.
• Protection provided by the borrowed antibodies
  is only TEMPORARY. It ends when they naturally
  degrade in the body.

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Active and Passive Humoral Immunity

• How is PASSIVE IMMUNITY acquired?
• NATURALLY The fetus is protected by the mothers
  antibodies which cross the placenta and enter the
  fetal circulation
• ARTIFICIALLY When we receive an IMMUNE SERUM
  (poisonous snakebites etc..) or we receive GAMMA
  GLOBULIN which is administered after exposure to
  Hepatitis.

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Cellular Immunity Lymphocytes

• Cellular Immunity
• T Cells are sensitized by binding to an antigen
  and a self protein displayed on the surface of a
  macrophage.
• Description of the CELLULAR Immune Response
• Immunocompetent T Cells are activated to form a
  CLONE by binding with a recognized antigen
  (like B Cells do)
• Clonal Selection of T Cells produce EFFECTOR T
  CELLS and MEMORY CELLS.
• Clonal Selection of B Cells produce PLASMA CELLS
  and MEMORY CELLS
• Antigen binding ALONE is NOT enough to sensitize
  T CELLS.What is the importance of ANTIGEN
  PRESENTATION
• Macrophages engulf the antigen and display parts
  of the antigen on their external surface in
  combination with one of their OWN proteins. These
  antigens are PRESENTED to T Cells so they will
  recognize them.

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Cellular Immunity - Lymphocytes

• Q Other than antigen presentation what is
  another important thing MACROPHAGES do for us
  during the Cellular Immune Response?
• A They release chemicals that activate T CELLS.
• CLASSES OF EFFECTOR T CELLS
• CYTOXIC T CELLS (Killer T Cells) Specialize in
  killing cancer cells, virus infected body cells,
  and cells involved in graft rejection.
• HELPER T CELL Regulatory T Cell Managers of
  the Immune System - They bind with a specific
  antigen being presented by a macrophage and they
  stimulate the production of other immune cells
  (Killer T Cells and B Cells)
• SUPPRESSOR T CELL Slows down or stops the
  activity of B and T Cells once the infection or
  attack by foreign cells has been conquered.

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Immune System Disorders

• The most important disorders of the Immune System
  are
• ALLERGIES
• IMMUNODEFICIENCIES
• AUTOIMMUNE DISEASES
• ALLERGIES Abnormally vigorous immune responses
  in which the immune system causes tissue damage
  as it fights off a perceived threat called an
  allergen that would otherwise be harmless to the
  body.
• TWO MOST COMMON TYPES OF ALLERGIES
• 1. Immediate Allergies Triggered by a flood of
  HISTAMINE which causes small blood vessels in the
  area to become dilated and leaky. This is what
  causes the symptoms of a runny nose, watery eyes
  and itching, reddened skin (hives).
• When the allergen is INHALED symptoms of asthma
  appear because smooth muscle in the walls of the
  bronchioles contracts, constricting the passages
  and restricting air flow
• TREATMENT Over the counter Antihistamines

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Immune System Disorders

• Immediate Hypersensitivity contd..
• Anaphylactic Shock The allergen DIRECTLY enters
  the blood and circulates rapidly through the
  body. Could come from bee stings, spider bites,
  penicillin etc.. Reactions could be life
  threatening
• Treatment Epinephrine
• Delayed Allergies Take longer to appear than
  acute allergies (1 3 days)..Reactions are NOT
  caused by histamines so antihistamines are NOT
  helpful..
• Most familiar examples involve skin contact
  with poison ivy, some heavy metals and certain
  cosmetic and deodorant chemicals.

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Immune System Disorders

• IMMUNODEFICIENCES
• Include both Congenital (at birth) and Acquired
• Congenital
• Severe Combined Immunodeficiency Disease (SCID)
  Most devastating Deficit of BOTH B and T Cells
  No immune protection (Boy in the Plastic
  Bubble)
• Acquired
• Acquired Immune Deficiency Syndrome (AIDS)
  Cripples immune system by destroying Helper T
  Cells resulting in the depression of cell
  mediated immunity.
• SEE A Closer Look on pp. 394 395

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Immune System Disorders

• Autoimmune Diseases
• The body doesnt recognize our self antigens as
  self and it produces antibodies and sensitized
  T Cells that attack its OWN tissues.
• More common in Women
• Most Common Autoimmune Disorders
• Multiple Sclerosis (MS) Destroys the myelin
  sheaths of the brain and spinal cord
• Graves Disease The Thyroid Gland produces
  excessive amts of Thyroxine.
• Systemic Lupus Occurs mainly in young Females
  Chronic Inflammatory Disorder Affects kidneys,
  heart, lungs and skin
• Rheumatoid Arthritis (RA) Destroys joints