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Immune System
 Important system that helps fight off pathogens
 What is a Pathogen?
Microorganism that causes infection or a disease:
Bacteria Viruses Fungi Protists/Parasites
 Made of many cells each with a specific job
including:
a. Lymphocytes –
White blood cells or WBC
Target specific Pathogens
Types of Lymphocytes
T cells Identify Pathogens by recognizing
their Antigens
B cells Produce chemicals called Antibodies
Macrophages –
Surround pathogen and digest or eat it
Also called Phagocytes
Types of Lymphocytes
 What are Memory Cells ?
Remember what type of antigens a pathogen has
Help immune system recognize the pathogen if it
invades our body again!!
AMAZING ! ! !
 What are the Types of T – Cells?
1. Natural Killers Cells
2. Cytotoxic Cells
* Destroy pathogens after they are marked by
antibodies
* Destroy cells that are infected with a virus
* Also recognize cancer cells and destroy them
ANTIGENS AND ANTIBODIES
 What are Antigens?
Special proteins on surface of cells and pathogens
They are recognized by the Immune System
 Why?
So that the White blood cells know which
pathogens they need to destroy!!!
 What are Antibodies?
Special proteins that recognize specific Antigens
on Pathogens
Mark the pathogens for destruction by WBC’s
Pathogens
 What are Pathogens?
Organisms that cause
disease
 Infectious diseases are?
Diseases that are caused
by pathogens .
 Staphyloccocus aureus
 Magnified 20,000X
 When you have an
 About 1 um in size
infectious disease
pathogens are inside your  What type of pathogen
body causing harm
is Staph?
BACTERIA
4 TYPES OF COMMON PATHOGENS

Can you guess what they are?
Viruses
Fungi
Bacteria Protists/Parasites
1. Viruses
Flu HIV Measles
2. Fungi
Athlete’s Foot
Candida albicans
Virus
Fungus
4 TYPES OF COMMON PATHOGENS
3. Bacteria
STAPH
Strep throat
Bacteria
4. Protists
Paramecium
Giardia
Giardia
The Immune System
• The immune system includes T cells and B cells.
• The cells work together to fight infections.
• How does the immune system work? Let’s find out!!
T-Cells have more than one job
One job may be to……………
What happens when a virus infects a cell?
What is another job of the T- cells?
So, why do B–cells produce
antibodies? Because……………..
Immunity
How does a person become immunized?
How does the Immune System work
T cells recognize bacterial or viral antigen.
Some T cells attack cells infected with pathogens.
Other T cells signal B cells to produce antibodies .
Antibodies attach to the antigens on virus or bacteria
(Lock & Key)
Antibodies help macrophages destroy the bacteria or
Two Types of Immunity
Active Immunity
Immune system produces antibodies
on its own in response to a pathogen
Passive Immunity
Antibodies are injected into a patient to
help prevent a disease from a pathogen
Vaccine
Contain a weakened pathogen that
stimulates production of antibodies without
causing the actual disease, or…………
Antibodies are already in the vaccine
Active Immunity
Both
The body makes
antibodies.
Memory cells
recognize antigens
from the pathogen.
Immunity may
last for years or
a lifetime.
Can prevent
diseases
May
involve an
injection
Passive Immun
Antibodies are
given; the body
does not make
antibodies.
Immunity can be
acquired from the
mother during
pregnancy.
Immunity lasts
only a few
months.
Review Questions
1. Question: What is the function of the immune
Answer:
system?
Helps fight off pathogens.
2. Question: Which 3 white blood cells or
lymphocytes help destroy pathogens?
Answer:
Macrophages, B cells and T cells
3. Question: What is an antigen?
Answer: Special protein on surface of
pathogens recognized by the
immune system
4. Question: What is an antibody?
Answer: Special protein in the immune
system that recognizes and attaches to
a specific antigen on a pathogen
and marks it for destruction.
5. Question: Explain the difference between
Active and Passive Immunity?
Answer: * In Active immunity the immune
system produces the antibodies.
* In Passive immunity the antibodies
are injected into a patient to
destroy the pathogens
6. Question: Which cells of the immune
system produce antibodies?
Answer:
B cells
7. Question: Which cells produce B cells?
Answer:
T cells
8. Question: What are memory cells?
Answer:
Remember what type of antigens a pathogen has
Help immune system recognize the pathogen if it
invades our body again!!
9. Questions: What are the 4 main functions of T-cells
Answer:
1. Destroy pathogens after they are marked by
Antibodies
2. Destroy cells that are infected with a virus
3. Also recognize cancer cells and destroy them
4. Stimulate B-cells to produce antibodies
10. Question: What are the 4 common pathogens?
Answer: Virus Bacteria Fungi Protists/parasites