Transcript THE IMMUNE SYSTEM

THE IMMUNE SYSTEM
What happens when we get sick?
Why do we get better?
K-W-L:
How does your body fight infection?
What do you
Know?
What do you
Want to know?
What have you
Learned?
What are some of the substances
or invaders that are targeted by the
immune system?
• Turn to your neighbor and share
your thoughts
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.
How does your body know when a
substance is an invader?
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
There are three lines of defense
against infection
The Immune System is the Third Line
of Defense Against Infection
First Line of Defense:
The outer layer of the body
• Primary goal: prevent organisms from
gaining access
Second line of defense:
Cells and proteins in our blood stream
• Primary goal: recognize, neutralize and
destroy invaders
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
Humoral Immunity produces antibodies
Antibodies produced by B cells of the Immune System
recognize foreign antigens and mark them for destruction.
On your paper, distinguish
between an antigen and an
antibody.
Cell-mediated Immunity
• Body’s defense
against its own cells
when they have
become cancerous or
infected by viruses.
• Important in fighting
infection caused by
fungi and protists.
T cells divide and differentiate
during cell mediated immunity
Killer
(cytotoxic
)
Tracks
down and
kills
antigens
Helper
Memory
Suppressor
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
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