Transcript The Immune System


Defined: microorganisms
that cause disease
• Viruses: turn cells into
virus making factories
• Bacteria: prokaryotes
that can release toxic
chemicals
• Fungi: pierce cells
and absorb the
nutrients
• Protozoans: single
cells protista
(eukaryotes)
• Parasites: grow and
feed on a host


Some carried by wind,
water, direct contact,
indirect contact…
Some carried by vectors
• Vector: object that
carries a pathogen
• Examples:
1) Malaria – mosquitos
carry the protozoan
2) Black Death – carried
by flea’s of mice
3) West Nile Virus –
carried by birds, but
spread by mosquitos
 1st
line of defense: physical barrier
 Oils & sweat destroy some pathogens
• Some cells burst
• Some cells shrivel
 Coat
the openings of the body
 Nose, mouth, ears, eyes, genitals, anus
 Lined
with cilia & sticky fluids to trap
pathogens
Job: Search & destroy
 Phagocytes: surround & engulf invaders

• Phagocytosis

Lymphocytes:
• T cells: destroy infected body cells
• B cells: Inactivate invaders
Blood
stream
 Complimentary
Proteins
• Weaken cell membrane
• Attract phagocytes
• Cause microbes to stick to wall of blood vessel
Antibodies
• Proteins made by B cells
• Attach to antigens found on
surface of cells
• How they help:
1) Bind to antigens of
pathogen (like handcuffs)
 Causes pathogens to clump
 Easy targets for phagocytes
2) Weakens the cell
membrane of pathogen
 Causes them to burst
B CELLS MAKE ANTIBODIES
ANTIBODIES ATTACH TO ANTIGENS OF THE PATHOGEN
Y
Y
Y
Y Y
Y
YY
YY
Y
Y
Blood
Stream
Y
Y
Y Y
Y
Y
Y
phagocyte
Y
Y
Y
ANTIBODIES CAUSE THE PATHOGENS TO CLUMP TOGETHER
PHAGOCYTE DESTROYS PATHOGENS
Y
Defense Proteins
• Interferon
– Cell becomes
infected by virus
– Infected cell
releases
interferon to
neighbors
– Healthy cell
(right) absorbs
the interferon
and creates
defense enzymes
– Healthy cell able
to fight virus
virus
Virus
RNA
New virus
New virus
New virus
New virus
Interferon
proteins
New virus
Vaccination
• Prevents infections (not a
cure)
• Vaccination process
– Weakened pathogen is
injected
– Antigens of pathogen
cause your immune
system to attack
• Immune system response:
– Production of memory
cells (for future
infections)
– Antibodies bind to
antigens (for current
infection)
• Goal: Speed up immune
response if you encounter
the actual virus