Transcript immune system - Doral Academy Preparatory

The Immune System
• Lymphatic system
• Defence system
• Immune system disorders
• Inside your body there is
an amazing protection
mechanism called the
immune system. It is
designed to defend you
against millions of
bacteria, microbes,
viruses, toxins and
parasites (pathogens)
that would love to invade
your body
THE LYMPHATIC SYSTEM
• A network of vessels and nodes
throughout the body
• Lymph is a pale, yellow interstitial fluid
(similar to blood plasma)
• Lymph serves to maintain fluid balance in
the body
• Lymph nodes contain lymphocytes and
macrophages (phagocytic monocytes)
which serve to trap & destroy bacteria
LYMPH NODES
• Viral and bacterial infections are by far the
most common causes of illness for most
people. They cause things like colds,
influenza, measles, mumps, malaria, AIDS
and so on. The job of your immune system
is to protect your body from these
infections. The immune system protects
you in three different ways:
1. It creates a barrier that prevents bacteria and
viruses from entering your body. (eg – skin)
2. If a bacteria or virus does get into the body, the
immune system tries to detect and eliminate it
before it can make itself at home and
reproduce. (eg – phagocytic white blood cells)
3. If the virus or bacteria is able to reproduce and
start causing problems, your immune system is
in charge of eliminating it. (eg – B and T cells)
The Immune System is the Third
Line of Defense Against Infection
Nonspecific Defenses
(FIRST LINE - Physical Barriers)
Figure 22.10
Nonspecific Defenses
(SECOND LINE - Phagocytes)
Figure 22.10
Nonspecific Defenses
(SECOND LINE - Immunological
Surveillance)
Natural killer T cells (cytotoxic T cells) destroy body cells that have become
cancerous or infected by viruses
Figure 22.10
Nonspecific Defenses
(SECOND LINE –
Complement System)
Figure 22.10
Specific Defences
(Antibody-Mediated Immunity)
• Antibodies are proteins that recognize
foreign substances (antigens) and try to
neutralize or destroy them.
• Antibodies are produced by
LYMPHOCYTES
• All white blood cells are known officially as
Leukocytes.
• White blood cells are not like normal cells
in the body - they actually act like
independent, living single-cell organisms
able to move and capture things on their
own.
•White blood cells behave very much
like amoeba in their movements and are
able to engulf other cells and bacteria.
• Many white blood cells cannot divide and
reproduce on their own, but instead have a
factory somewhere in the body that
produces them. That factory is the bone
marrow.
• Antibodies are
produced by white
blood cells.
• They are Y-shaped
proteins that each
respond to a specific
antigen (bacteria, virus
or toxin).
• Each antibody has a
special section (at the
tips of the two branches
of the Y) that is
sensitive to a specific
antigen and binds to it
in some way.
• When an antibody binds to the outer coat
of a virus particle or the cell wall of a
bacterium it can stop their movement
through cell walls. Or a large number of
antibodies can bind to an invader and
signal to the complement system that the
invader needs to be removed.
The immune system response
• Antigen triggers an immune response
• Activates T cells and B cells
– T cells are activated after phagocytes exposed
to antigen
• T cells attack the antigen and stimulate B
cells
• Activated B cells mature and produce
antibody
• Antibody attacks antigen
An Overview of the Immune
Response
Figure 22.15
Major types of T cells
• Cytotoxic (Killer) T cells – attack foreign cells –
pucture a hole in cell membrane
• Helper T cells – activate other T cells and B cells
• Suppressor T cells – inhibit the activation of T and
B cells – make sure normal tissue isn’t destroyed
• Memory T cells – remain in bloodstream and can
act quickly if antigen comes into blood again
Types of Immunity
Figure 22.14
IMMUNE SYSTEM DISORDERS
ALLERGIES
• An allergy is an
exaggerated response of
the immune system to a
harmless material (eg –
pollen, pet dander, grass,
peanuts, etc)
ALLERGIES
2 types of allergic
reactions:
• Immediate (or acute)
- occurs within seconds
of exposure –
disappears within 30
minutes
(eg) pets, nuts, pollen
• Delayed
- reaction is slower
and lasts longer
- T-cells are sensitized
by previous contact
(eg) cosmetics,
jewellery
What happens during an
immediate allergic reaction?
• Specialized antibodies trigger certain cells to
release histamines
• Histamines are chemicals that increase the
permeability of blood vessels
• Therefore, blood (mostly plasma with some
WBCs) leaks out of the vessels and into the
tissues – causing them to become red and
swollen
• Symptoms: itchy, puffy eyes, runny nose,
constriction of airways (asthma, or anaphylaxis)
What is anaphylaxis?
• Anaphylaxis is a
severe allergic
reaction to a specific
allergen – eg
peanuts, bee stings,
etc.
• Airways can close
almost immediately –
which can be fatal
• An injection of
adrenaline (Epi-pen)
is given
COMMON ALLERGENS
AUTOIMMUNE DISORDERS
• Your body identifies your own cells as
“self” cells
• Sometimes, T cells or antibodies make
mistakes and attack your own cells,
mistaking them for “non-self” cells
• An autoimmune disorder is the result
• EXAMPLES: rheumatoid arthritis, Type I
diabetes
RHEUMATOID ARTHRITIS
• A chronic
autoimmune disorder
• Characterized by
inflammation of the
joints
• Most common in
people 25-50 years
• Immune system
attacks bone,
cartilage, ligaments