AIM: How does our body defends us
from pathogens?
DN:
1.Explain what a pathogen is.
2.Give two examples of types of pathogens
and give a specific example for each type.
3.Will a Dr. give you antibiotics if you have a
cold? Why or why not?
HW: h/o tonsils
DO NOW QUIZ
1. Explain what a pathogen is.
2. Give two examples of types of
pathogens and give a specific
example for each type.
3. Will a Dr. give you antibiotics if
you have a cold? Why or why
not?
Pathogens
Any disease-producing
agent such as a virus,
bacterium, fungus, or
parasite.
1st Line of Defense
• Skin
–enzymes in sweat
• Mucus–trap pathogens
• Tears in eyes
– enzymes to destroy
pathogens
• Acid in stomach- inhospitable
to pathogens
2nd Line of Defense
The Immune
System
White Blood cells
• Large cells with a nucleus.
• Less numerous than RBC’s.
• Defenders of the body.
• Types:
– Phagocytes: engulf and destroy bacteria
– Lymphocytes: produce antibodies
Immune System
Made of proteins, cells, and
tissues that identify and
defend the body against
pathogens
How does our immune
system identify foreign cells?
Antigen
I.D. Tag
• A protein on the cell
• The ID tag identifies
the invader as not
belonging to the
body (non-self).
• This ID tag is called
an antigen.
Phagocytes
Engulf the Pathogens
Phagocytes:
White blood
Cells that
Eat a pathogen
Lymphocytes
Produce antibodies
• They can make
antibodies, which
are their weapons
against the foreign
antigens.
• Antibodies &
Antigens are both
proteins!!
Antibodies
Pathogen
Antibodies
Antigens
B Cells
• They are “Y”
shaped
proteins, made
Lymphocytes
by __________
• They are
weapons that
fight against
pathogens
How are nuts and screws similar
to antigens and antibodies?
Antibodies are made specifically to
match the shape of the antigen.
1 antigen = 1 antibody
What does this remind you of?
How do antibodies destroy
pathogens?
When the antibody
attaches to the
antigen, it breaks
open its cell
membrane
• Or, the antibody
attaches to the
antigen, and a
phagocyte will
know to engulf it
Our Immune System has a good
memory!
The first response is
relatively slow and
weak because time
is needed for enough
WBCs to form and
defeat the pathogen.
The second response
to the same pathogen
triggers a quicker and
stronger response.
** After the first response, the immune system “remembers”
specific pathogens by leaving behind WBCs that protect the
body for years (memory cells).