Defense against Infection

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Defense against Infection

• How Our Body Defends Against
• Pathogens

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What is the Immune System?

• Primary Defense against
• disease-causing organisms

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First Line Defense

• Skin (sweat, oil, waxes)
• Mucous membranes (mucus)
• Cilia/hair (nose, lungs
• Enzymes/Acids (lysozyme, stomach acid)
• MOST INVADERS ARE HANDLED THROUGH THIS INITIAL
  SECURITY SYSTEM

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Non-specific Immune Response- A Call to Arms!

• Begins with A breach in the first line
• Inflammatory Response
• Increased blood flow, clotting (if needed) SEAL
  OFF AREA
• Fever
• slows bacterial growth, promotes enzyme activity
• Complement formation (protein swords)

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Specific Immune Response- A Call to Arms!

• Cells and Tissues that recognize and attack
  foreign substances
• Include
• Lymph system includes Adenoids, Tonsils, Thymus,
  Lymph Nodes and Vessels, Spleen,
• Bone Marrow
• Lymphocytes WBC of immune system

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Lymphatic System

• Contains fluid (lymph) that leaks from
  circulatory system and filters it
• Vessels, nodes and organs
• Lymph nodes, Spleen
• Contain lymphocytes
• Pathogens in lymph are exposed to lymphocytes
  here.
• Adenoids and Tonsils are also lymph tissue
• Spleen
• Stores healthy blood cells, breaks down old blood
  cells

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Lymphocytes

• Cells that recognize invaders
• Bind to antigens on the surface of bacteria,
  pollen etc.
• Initiates the immune response
• B cells
• Made and mature in bone marrow
• T cells
• Made in marrow, mature in thymus

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Specific Immune Response

• Two part attack
• Cell mediated response T cells
• Humoral response B cells
• These occur simultaneously
• BOTH are started when pathogen is engulfed by a
  macrophage.

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The Troops

• Macrophage
• Helper T Cell
• Killer T Cell
• Virus

• B cell
• Complement
• Suppressor T Cell
• Memory T Cell
• Body Cell

Civilian
Enemy
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Initiation of the Attack
Virus
Macrophage
Cell
Virus looks for body cells to infect Macrophage
engulfs a virus - the battle begins
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The Macrophage - Enemy Recognition and Response

Antigen
Digests the virus Displays virus antigens on
surface
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When macrophage eats the bacteria it displays
antigens 1. Helper T binds to antigens 2.
Result chemical message released a.
more Helper T made, Killer T activate. b. Killer
T kill infected body cells
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Initiation of the Immune Response
Helper T cell binds to macrophage Initiates
communications to defense system
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Communications Expand the Defense Team
Chemical messages Increase Helper and
Killer T cells (cell mediated) B cells
manufacture specific antibodies.
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Cell Mediated
Killer T Cell
Killer T cells destroy infected body cells
(hosts) Virus exposed to defense team
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Humoral Response B cells

• B cells create antibodies and stimulate CP
• Antibodies can
• Bind to a surface antigen on bacteria and clumps
  them together so that macrophage can eat them
• Inactivate or destroy toxins
• Create complement proteins
• Put holes in pathogen cell membrane

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Humoral Response
Antibodies bind to antigens
Complement
B cell antibodies bind to virus antigens
Bound antigens consumed (macrophages)
Complement cells help phagocytes find enemy
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Memory Phase
Chemical messages Decrease T and B cells
Memory cells - Future Rapid Response
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Summary - Immune Response
1. Virus consumed by a macrophage 2. Macrophage
displays the virus antigens 3. Helper T-Cell
recognizes enemy . Call in the troops. 4. B
cells and Killer T Cells are manufactured 5. B
cells produce antibodies that bind the virus.
Killer T Cells destroy infected body cells. 6.
Suppressor T cells stop production of
defense. 7. Memory cells remain for future rapid
response.
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• Whenever T cells and B cells are activated, some
  become "memory" cells.
• The next time that an individual encounters that
  same antigen, the immune system is primed to
  destroy it quickly. Long-term immunity can be
  stimulated not only by infection but also by
  vaccines made from infectious agents that have
  been inactivated or, more commonly, from minute
  portions of the microbe.
• Short-term immunity can be transferred passively
  from one individual to another via
  antibody-containing serum similarly, infants are
  protected by antibodies they receive from their
  mothers (primarily before birth).

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B Cells

• B cells work chiefly by secreting soluble
  substances known as antibodies.
• Each B cell is programmed to make one specific
  antibody. When a B cell encounters its triggering
  antigen (along with various accessory cells), it
  gives rise to many large plasma cells. Each
  plasma cell is essentially a factory for
  producing that one specific antibody.

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