Immune System

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Immune System
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Review

• What is an immune system?
• The system in the body responsible for
  maintaining homeostasis by recognizing harmful
  from non harmful organisms and by producing an
  appropriate response
• What is immunity?
• The ability of the body to fight infection and/or
  foreign invaders by producing antibodies or
  killing infected cells
• Different types Natural Active, Natural Passive,
  Artificial Active, Artificial Passive

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How does the body fight infection/foreign
invaders?

• The Bodys THREE lines of Defense
• First Line of Defense The Skin
• Provides Physical and Chemical barriers
• Physical hard to penetrate, made of
  indigestible keratin
• Chemical tears, sweat, saliva and mucous
  (chemicals and enzymes in body fluids)

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First Lines of Defence
tears antibacterial
enzymes
saliva antibacterial enzymes
mucus linings traps dirt and microbes

• skin prevents entry

stomach acid low pH kills harmful
microbes
good gut bacteria
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White Blood Cells (Leukocytes)

• 1. Granulocytes (50-60) (basophil, eosinophil,
  neutrophil)
• release powerful granules that have chemicals
  inside that attack an intruder
• Basophil produce histamine (high during allergic
  reactions)
• Eosinophil (high in parasitic invasion)
• Neutrophil (aid in phagocytosis, high during
  bacterial infection)
• 2. Monocytes (7 )
• When activated become macrophages that engulf
  antigens
• 3. Lymphocytes (30-40 )
• T- Cells and B-Cells (Viral infections)
• All WBC are produced in the bone marrow as
  stem cells T-cells migrate to the thymus
  thats where they mature
• WBC are found in lymph nodes, spleen liver

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Second Line of Defense Nonspecific Immune
Response

• These are defenses the body uses no matter what
  the invader may be. These defenses include
• Phagocytosis done by Macrophages
• Inflammation - caused by release of Histamine
  from leukocytes
• Fever caused by histamines. The fever (high
  temp) kills invaders by denaturing their proteins.

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Phagocytosis

• Stages in phagocytosis
• Phagocyte detects chemicals released by a foreign
  intruder (e.g. bacteria)
• Phagocyte moves up the concentration gradient
  towards the intruder
• The phagocyte adheres to the foreign cell and
  engulfs it in a vacuole by an infolding of the
  cell membrane.
• Lysosomes (organelles which are rich in digestive
  enzymes found in the phagocytes cytoplasm) fuse
  with the vacuole release their contents into it.

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Phagocytosis

• The bacterium is digested by the enzymes, and the
  breakdown products are absorbed by the phagocyte.
• During infection, hundreds of phagocytes are
  needed.

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Injury

• Chemical signals are released by the foreign
  invader
• Chemicals cause capillaries to dilate thus
  increasing blood flow
• Basophils flow through the blood stream and
  gather to the site of infection and release
  histamine (histamine cause inflammation and
  increase blood flow)
• This brings neutrophils and monocytes to the site
• Neutrophils release chemicals that engulf and
  kill antigens
• they have a short lifespan but are constantly
  supplied
• dead neutrophils form pus
• macrophages engulf and kill antigens and dead
  neutrophils
• Inflammation response (swelling, heat, redness
  pain)
• TREATMENT???

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Fever

• The hypothalamus responds to a chemical signal
  caused by the presence of a pathogen
• The signal makes the hypothalamus increase the
  normal set point for normal temperature in the
  body from 37?C t0 39?C (Optimal)
• WHY?
• Some hypothesize that immune cells function more
  effectively at that temperature
• Invaders/pathogens are not so equipped with
  dealing with heat (High temp. denatures their
  proteins)

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Third Line of Defense Specific Immune Response

• This is a specific response to a specific
  pathogen/antigen.
• The response involves lymphocytes and the
  creation of Antibodies.
• There are 2 types of lymphocytes
• T-cells identify and attack foreign
  substances, regulate B-cell production and stop
  the immune response
• B-cells produce antibodies and are
  programmed to respond to a specific antigen

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Antigens

• all cells have surface markers called antigens.
• body can recognize these as self or non-self
  (foreign)

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Specific response

• Lymphocytes detect presence of foreign antigens
• Stimulated to produce
• specific proteins called
• antibodies.

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How an antibody operates/works?
Deactivation of a bacterium by an antibody.
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The Pathway of Specific Immune Response
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Immune Response Explained

1. Antigen infects cells.
2. Macrophage ingests antigen and displays portion
   on its surface.
3. Helper T- Cell recognizes antigen on the surface
   of the macrophage and becomes active.
4. Active Helper T-Cell activates Cytotoxic T-Cells
   and B-Cells.
5. Cytotoxic T-Cells divide into Active Cytotoxic
   T-cells and Memory T Cells.
6. Active Cytotoxic T-Cells kill infected cells.
7. At the same time, B-Cells divide into Plasma
   Cells and Memory B- Cells.
8. Plasma cells produce antibodies that deactivate
   pathogen.
9. Memory T and Memory B cells remain in the body to
   speed up the response if the same antigen
   reappears.
10. Supressor T-Cells stop the immune response when
    all antigens have been destroyed.

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Cellular Immunity .vs. Antibody Immunity
Cellular Immunity
Antibody or Humoral Immunity

• Carried out by T-Cells
• Infected cells are killed by Cytotoxic T Cells.

• Carried out by B-cells
• Antibodies are produced and dumped into blood
  stream.
• Antibodies bind to antigens and deactivate them.

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Immune Response Summary
Displays copy of antigen on surface of cell
Antibody Immunity
Cellular Immunity
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What happens during an allergic reaction?

• Anaphylaxis or anaphylactic shock
• This is the sudden and severe allergic reaction
  to a substance that can cause death.
• During an allergic reaction, antibodies cause
  histamines to be released from certain cells. In
  addition blood vessels dilate which causes a
  decrease in blood pressure and heart rate.
• Histamines cause
• a. Swelling of tissues
• b. Release of fluids (runny noses and eyes)
• c. muscle spasms (some cases)
• Treatments for Allergies
• Avoidance of material especially food.
• Epinephrine epi pen
• Antihistamines -- benadryl