Download The Immune System

The Immune System
The Body’s Defense
• Pathogens are
everywhere.
• We stay healthy because
our body has defenses to
keep pathogens out.
• The immune system
fights infection through
the production of cells
that inactivate unwanted
cells
• A lymphocyte engulfing
an invader
Nonspecific Defenses fight or
defend against any pathogen
First line of defense:
–
–
–
–
Skin
Mucus
Sweat
Tears
Second line of defense:
inflammatory response
fever
interferons (fight viruses)
Specific Defenses guard against
certain invaders
• When a pathogen
gets past the body’s
nonspecific defenses,
the immune system
attacks.
• The antigen (invader)
triggers the immune
response.
• Future attacks will be
met by memory cells
Organs of the Immune System
Humoral Immunity-B cells
• B lymphocytes (B cells) provide immunity
against antigens and pathogens in body fluids
• B cells recognize invader and produce large
numbers of plasma cells and memory B cells
• Plasma cells release antibodies
– Antibodies are proteins that recognize & bind to
antigens
– As antibodies overcome infection, plasma cells die off
and stop producing antibodies
– Memory B cells remain in blood stream so they can
make plasma cells immediately if ever exposed to the
same pathogen again
Cell Mediated Immunity-T Cells
• Killer T cells track down and destroy bacteria,
fungi, protists, or other foreign tissue.
– Primary defense against the body’s own cells when
they have become cancerous or infected by
pathogens
• Helper T cells produce memory T cells.
• Memory T cells will attack if the same pathogen
ever returns.
• Suppressor T cells shut down the killer T cells
when the infection is under control.
HIV attacks T cells
• HIV (Human
Immunodeficiency
Virus) attacks the
body’s T cells.
• The immune system
is disabled.
• Victim is not able to
fight infection
• HIV eventually
causes AIDS
Vaccines
• Edward Jenner invented first vaccine in
1769
– Injected boy with cowpox virus (weak similar
virus to smallpox)
– Later injected with deadly smallpox virus.
• Boy had immunity to the virus
• Vaccines are weakened or “killed” virus or
bacteria pathogen.
• The body responds by creating an
immunity to the pathogen (antibodies)