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The Immune System
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Terms to know
• Pathogens--- organisms that cause
disease
• Antigen--- a marker molecule on a
cell that the immune system uses to
recognize a pathogen
• Antibody--- a chemical that helps
destroy a specific kind of pathogen by
locking onto a specific marker
molecule
Three
lines
of
defense
1. Barriers
•
•
•
Skin—forms a physical and chemical
barrier
Breathing passages---mucus and cilia
trap and remove pathogens (sneeze or
cough)
Mouth and Stomach---most pathogens
you swallow are destroyed by chemicals
in your salivia or stomach acids
2. Inflammatory response
•
•
•
Fluid and certain types of white blood
cells leak from blood vessels into
nearby tissues.
The white blood cells (phagocytes) then
fight the pathogen.
During the inflammatory response, the
affected area becomes red, swollen,
and warm. Fever may also occur.
3. Immune response
• The cells of immune system can
distinguish between different kinds of
pathogens. The immune system cells
react to each kind of pathogens with a
defense targeted specifically at that
pathogen.
• White blood cells that target specific
pathogens are called lymphocytes.
Two major kinds of lymphocytes
1. T-cells identify pathogens by
recognizing their antigens
2. B-cells produce chemicals
called antibodies
HIV
• Human Immunodeficiency Virus
• Spread through bodily fluids only
• HIV works like a trojan horse----HIV
sneaks inside the T cell and destroys it.
HIV goes undetected from the immune
system.