THE IMMUNE SYSTEM

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THE IMMUNE SYSTEM

• What happens when we get sick?
• Why do we get better?

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K-W-L How does your body fight infection?
What do you Know? What do you Want to know? What have you Learned?

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What are some of the substances or invaders that
are targeted by the immune system?

• Turn to your neighbor and share your thoughts

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Foreign Invaders

• Any non-self substance capable of triggering an
  immune response is known as an antigen.
• An antigen can be a whole non-self cell, a
  bacterium, or a virus.

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How does your body know when a substance is an
invader?
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ANATOMY OF THE IMMUNE SYSTEM

• The immune system is localized in several parts
  of the body
• immune cells develop in the bone marrow and
  thymus
• immune responses occur in the secondary organs

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There are three lines of defense against infection
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First Line of DefenseThe outer layer of the
body

• Primary goal prevent organisms from gaining
  access

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Second line of defense Cells and proteins in
our blood stream

• Primary goal recognize, neutralize and destroy
  invaders

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Third Line of Defense The Immune Response

• Two types of cells are involved
• B cells provide immunity against antigens and
  pathogens in the body fluids
• This is called humoral immunity
• T cells provide defense against abnormal cells
  and pathogens inside living cells
• This is called cell-mediated immunity

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Humoral Immunity produces antibodies
Antibodies produced by B cells of the Immune
System recognize foreign antigens and mark them
for destruction.
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On your paper, distinguish between an antigen and
an antibody.
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Cell-mediated Immunity

• Bodys defense against its own cells when they
  have become cancerous or infected by viruses.
• Important in fighting infection caused by fungi
  and protists.

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T cells divide and differentiate during cell
mediated immunity
Killer (cytotoxic) Helper Memory Suppressor
Tracks down and kills antigens Activates the killer T cells and B cells Similar to B cells will cause a secondary response if body is invaded by the same antigen twice Shut down the killer cells once the pathogen is brought under control
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Check your understanding Complete the Learned
Column of your K-W-L chart

• First, generally describe the function of the
  immune system.
• Next, list following cells on your paper
• B cells, plasma cells, helper T cells, killer T
  cells and macrophages
• Write a description of the function(s) of each
  type of cell in preventing or fighting disease