Download The Immune System

The Immune System
11.2
Immune System
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The immune system is composed of
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the bone marrow
the thymus gland
lymph vessels
lymph nodes
spleen
tonsils
Immune System
The Immune Response
The immune response consists of both
specific and non-specific kinds of defense
 The non specific response acts in a
general fashion against all invaders
 The specific response is very, very
selective. It only responds to a particular
kind of foreign substance
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Non-Specific Defenses
Against Infection
First Line of Defense
Skin- virtually impenetrable if unbroken
 Tears and saliva have fluids that contain
lysozymes that destroy cell walls of
bacteria
 Respiratory system has cilia to remove
particles
 Stomach secretes acidic gastric juices
 Normal intestinal E. coli compete with
invaders
 PHYSICAL LINE OF DEFENSE
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Second Line of Defense
Can be mobilized if the invader takes up
residence within the body.
 Leukocytes, or white blood cells, may
engulf invading microbes or produce
antibodies
 Nonspecific defence mechanisms rely
mainly on the process of phagocytosis, the
ingestion of invading microbes
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PHAGOCYTOSIS
Macrophages
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When a foreign particle penetrates the
skin through an injury, special
leukocytes, known as monocytes,
migrate from the blood into the tissues,
where they form macrophages (meaning
“big eaters”)
They extend long protrusions, called
pseudopods, that attach to the surface of
the invading microbe, engulf and destroy
it
Phagocytic White Blood Cell
Neutrophils
Another phagocytic response, white blood
cells called neutrophils are attracted to
chemical signals given off by cells that
have been damaged by microbes.
 Neutrophils squeeze out of capillaries
(chemotaxis) and migrate to the infected
tissue
 Neutrophils are phagocytic.
 The remaining fragments of protein, dead
white blood cells and digested invader are
called pus
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Inflammatory Response
Initiated due to physical injury
(nonspecific response)
 Results in swelling, redness, heat and pain
 Injured cells emit chemicals that stimulate
the production of phagocytic white blood
cells and increase their release into the
blood stream
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Fever
When your body is invaded by infectious
organisms (cold or flu), neutrophils and
macrophages digest the invaders and
release chemicals into your bloodstream
 This signals the hypothalamus to reset
the body’s thermostat to a higher
temperature –about 40 C making it
difficult for harmful bacteria to survive
 A fever of above 41 C can become
dangerous and human cells can not
survive temperatures above 43 C
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Leukocytes
Neutrophils
Phagocytic
Most
numerous
Monocytes
Macrophages
Phagocytic
“Big Eaters”
Basophils and
Eosinophils
Allergic reaction
Parasitic infection
Lymphocytes
T-cells
• Helper
• Killer
• Suppressor
• Memory
B-cells
Specific Defense Against
Infection
Third Line of Defense
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Specific Immunity
Complement proteins are plasma proteins that
help defend against invading microbes by
tagging the microbe for phagocytosis,
puncturing cell membranes or triggering the
formation of a mucous coating
Lymphocytes
Lymphocytes are a type of white blood cell
that produces antibodies
 An antibody is a protein molecule that
protects the body from invaders
 All cells have special markers located on
their cell membranes
 Cell membranes of bacterium and the
outer coat of a virus contain many
different antigens
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Antigen – Antibody Reactions
Antibodies are Y-shaped proteins
engineered to target foreign invaders
 Antibodies are specific (example: an
antibody produced against the influenza
virus is not effective against measels)
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T cells
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There are four types of T-cells in our
bodies
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killer T
memory T
suppressor T
helper T
Helper T-cell
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produced in the bone marrow & stored in
the thymus gland, giving its name
it travels in the blood acting as a sentry
identifying invaders by their antigens
once identified another T-cell (helper)
releases a chemical called interferons to
call other WBC into action and
lymphokines which activate the B-cells
Killer T-cells
If cells are infected by bacteria or viruses,
the killer T will destroy the human cell and
all that is in it by secreting toxins
 A small sacrifice is made for the good of
all
 Often involved when we reject organ
transplants
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Suppressor T-cells
This cell signals the immune system to
shut down after the battle has been won
 The helper T & suppressor regulates and
maintains a balance of antibodies &
responses to contain invaders by
decreasing B and T cells as needed
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Memory T-cells
remain around to secrete chemicals for
macrophages if antigen re-enters body
 remember the shape of invading antigens
so that when you are infected again the
immune response is immediate
 this forms the basis of vaccines
 Any ideas how vaccines would work?
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B cells
Are activated in the presence of foreign
antigens to begin making antibodies in the
lymph system
 Antibodies only bind to specific antigens
and will coat the antigen, making the
invader easier for detection and
engulfment by phagocytic cells
(macrophages)
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Additional Help
Antibiotics- chemicals that interfere with
the functioning of bacteria
 Vaccinations- here we are given dead or
weakened foreign antigens so that our
body can create B and T cells that will help
us out if we ever really do contract the
disease.
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Production of Antibodies
Things that can go wrong
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Immunodeficiency Diseases
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individuals are unable to protect themselves
against diseases
Autoimmune Diseases
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body has difficulty identifying self from non
self cells so body will attack its own cells
may be genetic or environmental
rhumatoid arthritis, multiple sclerosis, lupus,
diabetes mellitus, graves disease
Things that can go wrong
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Allergies
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hypersensitivity to environmental antigens
cause sneezing, runny nose, coughing, even
anaphlyatic shock
Human Immunodeficiency Virus (HIV)
HIV
outside layer is very similar to those of
helper t cells
 Virus enters by receptor-mediated
endocytosis
 Once inside of the t cells, it makes
multiple copies of itself, later rupturing,
releasing the copies to infect other helper
t cells.
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HIV