Connect!
• Have you ever had…
the measles?
the mumps?
a cold?
the flu?
• Why/why not?
• What words come to mind when you see
the term “Immune System”?
B. Immune System – Fighting to Stay Healthy
 Homeostasis is constantly threatened
by disease
Inheritance
Toxins
Causes of
Disease
Unhealthy
Lifestyle
Risky
Behaviors
Pathogens
♦ the immune system which consists of
lymph, mucus, lymph nodes, and white
blood cells allows us to effectively combat
invaders
Pathogens (the bad guys)
 There are many potentially dangerous
disease-causing organisms called
pathogens in our air, water, and food such
as
1. Viruses
*composed of a nucleic acid and a protein
coat
*spread easily
*examples include common cold, flu, and
chickenpox
2. Bacteria
*one-celled organisms
*some bacteria cause illnesses such as
strep throat, syphilis, and food poisoning
3. Fungi
*organisms that eat by absorbing food
*examples include athlete’s foot fungus
and ringworm
4. Parasites
*include animals and one-celled
organisms that live and feed on other
organisms
*examples include leeches and
tapeworms
chunk!
• Name 5 causes of disease.
• What are the parts of the immune
system?
• What is the job of the immune system?
• Define pathogen.
• Name 4 types of pathogens.
• Give characteristics and examples of
each type of pathogen.
Fighting the Pathogens
 All cells have recognition molecules on
their membranes called antigens.
 The immune system can usually tell the
difference between its own body cells and
“non-self” cells such as pathogens
because of these antigens.
 Antigens on the surface of pathogens
trigger a response from the immune
system.
White Blood Cells
♦ Some cells are specialized to surround
and engulf pathogens.
 Other white blood cells produce
antibodies (proteins that either attack the
pathogens or mark them for killing).
 Antibodies “recognize” their antigen by
matching molecule shape.
Pathogens have antigens.
Our bodies have antibodies
against invader antigens.
♦ The marked invaders may then be
engulfed by yet other white blood cells.
♦ Most white blood cells and antibodies disintegrate after
defending the body, but some specialized white blood
cells called memory cells remain. They are also
known as B-cells.
♦ Memory cells are capable of quickly dividing and
producing more antibodies of the same kind to fight off
later invasions of the same microbes (microscopic
organisms).
Chunk!
• What are recognition molecules on the
surface of cells called?
• What triggers an immune response?
• What kind of cells engulf pathogens?
• What are antibodies and how do they
work?
• What are memory cells?
• Why don’t you get a sickness twice?