Download IMMUNE SYSTEM

IMMUNE SYSTEM
• Viruses, bacteria and other
germs are all around us.
Most of the time, a healthy
immune system keeps us
well.
• The purpose of the immune
system is to keep infectious
micro-organisms, such as
certain bacteria, viruses,
and fungi, out of the body,
and to destroy any
infectious micro-organisms
that do invade the body.
• The immune system
is made up of a
complex and vital
network of cells and
organs that protect
the body from
infection.
• The organs involved
with the immune
system are called
the lymphoid
organs. They
release lymphocytes
(a certain type of
white blood cell).
What are lymphocytes?
• Lymphocytes - a type of infection-fighting white
blood cell and are vital to an effective immune
system. Lymphocytes "patrol" the body for
infectious micro-organisms.
• Certain cells will become lymphocytes others
phagocytes. Once the lymphocytes are formed,
some will mature and become "B" cells others
will finish their maturation and become "T"
cells.
First Line of Defence: SKIN
• The Body's most important Non-specific
Defence is the SKIN. Unbroken Skin provides
a continuous layer that protects almost the
whole body. Very Few Pathogens can
penetrate the layers of dead cells at the skin's
surface.
• Oil and sweat glands at the surface of the skin
produce a salty and acidic environment that kills
many bacteria and other micro-organisms.
.
First Line of Defence: Mucus,
Cilia and Hairs
• HAIRS -FILTER microbes and dust in nose.
• MUCOUS MEMBRANES are Epithelial Tissues that
protect the interior surfaces of the body that may be
exposed to pathogens.
• Mucous membranes serve as a barrier and secret
MUCUS, a sticky fluid that traps pathogens.
• Many secretions of the body, including mucus, saliva,
sweat, and tears, contain LYSOZYME, an enzyme that
breaks down the cell wall of many bacteria.
• MUCUS, CILIA, and HAIRS in the Nose and Throat trap
Viruses and Bacteria. Cilia in the Trachea trap Bacteria,
Pathogens that make it to the Stomach, which are then
destroyed by Stomach Acid and Digestive Enzymes.
The Second Line Of Defence:
THE INFLAMMATORY RESPONSE
• Despite the initial Defences of the Skin
and Mucous Membranes, Pathogens
sometimes enter the Body.
• When Pathogens enter the Body, The
Body's Second Line of Defence acts when
tissues are Injured.
• The injured cells release a Chemical
called HISTAMINE, which starts a series
of changes called the Inflammatory
Response.
• The inflammatory response is a non-specific defence
reaction of the body to tissue damage.
• Histamine increases blood flow to the injured area and
increases the permeability of the surrounding capillaries,
as a result, Fluid and White Blood Cells (WBC) to leak
from blood vessels into nearby tissue.
• Pathogens are attacked by phagocytes, which are white
blood cells that engulf and destroy pathogens by
phagocytosis.
How Our Bodies Fight Disease
• White blood
cells: defend
against germs
• The immune system
is made up of many
different kinds of
white blood cells.
White blood cells
work together to
protect us against
disease-causing
germs
MACROPHAGES
• Macrophages
identify germs:
When a germ
invades our
bodies,
macrophages
gobble up the
germ and display
its surface shape,
or antigen, for
other immune
cells to see.
HELPER T CELLS
• Helper T cells:
direct the
defence.
• Helper T cells spot
the foreign antigen
on the macrophage
and begin to
multiply. They alert
other white blood
cells and direct the
body's defence.
B CELLS
• B cells: make
antibodies
• B cells start to
make chemicals
called antibodies.
Antibodies lock
onto foreign
antigens making it
easier for other
immune cells to
destroy them
KILLER T CELLS
Killer T cells:
destroy germs
Alerted by helper T
cells, killer T cells
multiply and
destroy the
invading germs.
Working together,
our white blood
cells can usually
destroy invading
germs
IMMUNITY
• Not only does the immune system provide
protection from infection through natural
barriers, but it also adapts itself to provide
immunity against infection by
"remembering" the infectious microorganism from a previous exposure.
• The degree and duration of immunity
depend on the type and amount of antigen
and how it enters the body.
Natural Immunity Acquired Immunity
• Is created by the
• Or active immunity: Develops
body's natural
through exposure to specific
barriers, such as the
foreign micro-organisms,
skin, and protective
toxins, and/or foreign tissues),
substances in the
which are "remembered" by
mouth, the urinary
the body's immune system.
tract, and on the eye
When that antigen enters the
surface. Another type body again, the immune
of natural immunity is system "remembers" exactly
in the form of
how to respond to it. When
antibodies passed on that same person is exposed
from mother to child.
again the immune system
triggers antibodies to fight the
disease.
VACCINES
• All types of
vaccine stimulate
the body's own
immune system to
produce
antibodies and
cells in the same
way as the
disease would but
without the
dangers of the
disease.
Vaccines can be made up of:
•Killed bacteria.
• Weakened viruses or bacteria.
•Parts of the bacterium or virus.
•Inactivated (harmless) toxins.
•Vaccines are given at a young age to protect
against diseases.
•Following the introduction of vaccination there has
been a dramatic decrease in childhood deaths and
an increase in life expectancy.
•Each year vaccines prevent up to three million
deaths [worldwide] and 750,000 children are saved
from disability"
HIV
• To become infected with
HIV, one or more virus
particles must enter the
body
• Once inside the body they
need to find their way to
susceptible cells, where the
HIV life-cycle begins.
• T cells are the main cells
which HIV targets and
infects but they also target
macrophages.
•The first step of the HIV life cycle is
binding to the cell membrane.
•Followed by membrane fusion, to get the virus
particle's contents into the host cell.
•Then follows reverse transcription of the HIV's
genome from RNA into DNA, and its integration into
the host genome.
•Once integrated the virus can lie low or can begin
the production of new viral RNA, turning the cell into
a HIV factory
• This is followed by assembly, budding, and
maturation
•Then the new HIV particles are packaged up and
sent out to infect new cells.