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The Body Defenses

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									The Body’s Defenses
     Chapter 40
               Objectives
• Describe how skin & mucous membranes
  defend the body.
• Compare the inflammatory response with
  the temperature response.
• Identify proteins that kill or inhibit
  pathogens.
• Analyze the roles of white blood cells in
  combating pathogens.
             Key Terms
• Pathogen          •   Complement System
• Mucous Membrane   •   Interferon
• Inflammatory      •   Neutrophil
  Response          •   Macrophage
• Histamine         •   Natural Killer Cell
                  Pathogens
• A pathogen is a disease causing agent.
• Examples:
  –   Harmful bacteria
  –   Viruses
  –   Fungi
  –   Protists
First Line of Defense

     Non - Specific
        First Line of Defense
• Skin
• Nearly impenetrable barrier
• Reinforced w/ chemical weapons to inhibit
  pathogen growth
  – Oil
  – Sweat: contains an
  enzyme which digests
  bacterial cell walls
          First Line of Defense
• Mucous Membranes are layers of tissue that
  produce a sticky, viscous fluid called
  mucous.
• Examples:
  –   Digestive System
  –   Nasal Passages
  –   Lungs
  –   Respiratory Passages
  –   Reproductive Tract
    What Happens if A Pathogen
    Gets Through the First Line?
•    Four things happen
    1.   Inflammatory Response
    2.   Temperature Response
    3.   Special Proteins that kill or inhibit pathogens
    4.   White Blood Cells, which attack & kill
         pathogens
     Second Line of Defense
   The Inflammatory Response
• An inflammatory response is a series of
  events that suppress infection & speed
  recovery.
• Injured cells release chemicals, including
  histamine
  – Causes local blood vessels to dilate, increasing
    blood flow.
  – Increase blood flow brings more white blood
    cells (WBCs)
Inflammatory Response
      Second Line of Defense
      Temperature Response
• Body temperature increases several degrees
  above the normal value.
• Fever is helpful b/c many disease-causing
  bacteria do not grow well @ high
  temperatures.
• Extremely high temperatures are dangerous
  b/c it can destroy important cellular
  proteins.
      Second Line of Defense
         Special Proteins
• Complement System – consists of about 20
  different proteins.
  – Proteins circulate in the blood & become active
    when they encounter certain pathogens.
  – Some proteins form a membrane attack
    complex (MAC), which punches a hole in the
    cell membrane, causing the cell to leak & die.
       Second Line of Defense
          Special Proteins
• Interferon – a protein released by cells
  infected w/ viruses.
  – Causes nearby cells to produce an enzyme that
    prevents viruses from making proteins & RNA.
      Second Line of Defense
        White Blood Cells
• Most important counterattacks in the second
  line of defense
• 3 Types
  – Neutrophils
  – Macrophages
  – Natural Killers
• Each kind uses a different mechanism to kill
  pathogens
              White Blood Cells




                         Natural Killer Cell

Macrophages
              White Blood Cells
• Neutrophils – engulfs &
  destroys pathogens
   – Most abudent, kill the
     pathogen &
     themselves; can
     squeeze btwn cells in
     the walls of capillaries
          White Blood Cells
• Macrophages –
  ingest & kill
  pathogens
   – Clear dead cells
     & other debris;
     concentrated in
     the spleen &
     lungs
           White Blood Cells
• Natural Killer Cells – attacks cells infected
  w/ pathogens
  – Punctures the cell membrane causing water to
    rush in, in turn causing swelling. The cell will
    eventually burst.
  – Best defense against cancer
                  Review
• Often take the first stand during an infection. They attack
  any invaders in large numbers, and "eat" until they die.

• Are slower to respond to invaders than the granulocytes,
  but they are larger, live longer, and have far greater
  capacities. Macrophages also play a key part in alerting the
  rest of the immune system of invaders.

• Are "eater" cells and devour intruders, like the
  granulocytes and the macrophages. And like the
  macrophages, the dendritic cells help with the activation of
  the rest of the immune system.
Immune Response
Chapter 40 Section 2
               Objectives
• List four kinds of immune system cells, and
  describe their functions.
• Describe how white blood cells recognize
  pathogens.
• Identify the role of higher T cells in the
  immune response.
• Compare the role of T cells with that of B
  cells in the immune response.
                 Key Terms
•   Cytotoxic T cell
•   B cell
•   Helper T cell
•   Antigen
•   Plasma cell
•   Antibody
What happens when pathogens
occasionally overwhelm your
body’s nonspecific defenses?

      Third Line of Defense
             Specific
         Third Line of Defense
          Immune Response
•   Not localized in the body
•   Not controlled by a single organ
•   More difficult to evade
•   Consists of individual cells that rush
    throughout the body to combat specific
    invading pathogens
      Cells Involved in the Immune
                Response
• Four main types of White Blood Cells
  (WBCs)
  – Macrophages: consume any pathogen &
    infected cell
  – Cytotoxic T cells: attack & kill infected cells
  – B Cells: label invaders for later destruction by
    macrophages
  – Helper T cells: activate both cytotoxic T cells &
    B cells
     • B cells & T cells respond only to pathogens for
       which they have a genetically programmed match
                Antigens
• An antigen is a substance that triggers an
  immune response.
• Typically include proteins & other parts of
  viruses or pathogen cells.
• Present on the surface of the infected body
  cell
• WBCs are covered w/ receptor proteins that
  bind to specific antigens
Antigens
Killer T-Cells
Memory Cells
Disease Transmission &
      Prevention
    Chapter 40 Section 3
               Objectives
• List five ways diseases can be transmitted
  to humans.
• Analyze how the body produces immunity
  to pathogens.
• Describe how vaccines produce immunity
  to pathogens.
                Key Terms
•   Koch’s postulates
•   Immunity
•   Vaccination
•   Vaccine
•   Antigen shifting
          5 Different Ways of
         Disease Transmission
1.   Person-to-Person contact (communicable)
2.   Air
3.   Food
4.   Water
5.   Animal bites
       Long-Term Protection
• The specific immune response is very
  powerful, & can be a long-lasting defense
• B cells & T cells become memory cells that
  continue to patrol your body’s tissues.
• If the pathogen ever appears again, memory
  cells activate antibody protection.
• Second exposure to the same pathogen
  causes a sharp increase in antibody
  concentration.
        Resistance to Disease
• Resistance to a particular disease is called
  immunity.
• Vaccination is a medical procedure used to
  produce immunity.
• A vaccine is a solution that contains a dead
  or weakened pathogen or genetic material
  from a pathogen.
  – Triggers an immune response against the
    pathogen w/o symptoms of infection
           Antigen Shifting
• You can get the flu even if you have already
  been infected or vaccinated.
• Influenza viruses constantly mutate over
  time
• Viruses produce new antigens that you
  immune system does not recognize
• W/ subsequent exposure to the virus, your
  body must make new antibodies
Disorders of the Immune System

        Chapter 40 Section 4
              Objectives
• Describe several auto-immune diseases.
• Summarize how HIV disables the immune
  system.
• List five ways HIV is transmitted.
• Identify causes of an allergic reaction.
               Key Terms
•   Autoimmune disease
•   AIDS
•   HIV
•   CD4
•   Allergy
        Autoimmune Diseases
• In an autoimmune disease, the body
  launches an immune response against its
  own cells, attacking body cells as if they
  were pathogens.
Common Autoimmune Diseases
                  AIDS
• Before 1981 AIDS was unknown
• Between 1981-2000, more than 448,000
  Americans died of AIDS
• Total number of people living w/ HIV in the
  US has increased to more than 850,000
• AIDS is a disease caused by HIV
                       HIV
• Many scientist think
  HIV evolved from a
  virus similar to one
  that infects nonhuman
  primates in Africa.
• A mutation enables
  HIV to recognize a
  receptor protein called
  CD4 on some human
  cells.
                   HIV
• HIV enters WBCs by binding to CD4.
• HIV usually invades helper T cells, which
  begin to produce HIV soon after infection.
• When helper T cells die, the immune
  system gradually weakens & becomes
  overwhelmed by pathogens that it would
  normally detect & destroy.
            Testing for HIV
• Antibodies for HIV can be detected in
  blood.
• AIDS is diagnosed on several factors,
  including a helper T cell count less than 200
  cells/mL of blood.
Onset of AIDS
                    AIDS
• Time btwn HIV & AIDS can exceed 10
  years
• In the US, the number of deaths caused by
  AIDS:
  – 1996 – 38,000
  – 1997 – 22,000
  – 2000 – 15,000
• This is not due to a decrease in infections,
  rather more effective drug therapies, which
  postpone onset of the disease.
          Transmission of HIV
•   Contact with infected body fluids
•   Sexual contact
•   Sharing needles
•   Transfusions (many years ago)
•   Pregnant or nursing mothers to infants from
    blood & breast milk
    How HIV is NOT Transmitted
•   Through the air
•   Toilet seats
•   Kissing
•   Handshaking
•   Mosquitoes & ticks
•   HIV has been found in saliva, tears & urine
    however, they usually contain too few HIV
    particles to cause infection
            Allergic Reactions
• An allergy is the body’s inappropriate
  response to a normally harmless antigen.
• Include:
  –   Pollen
  –   Feces of dust mites
  –   Fungal spores
  –   Substances found in some foods & drugs

								
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