Every organism's body is being attacked and invaded constantly by viruses and by living organisms such as bacteria, protists, fungi, and multicellular parasites. Without defenses against the damage, diseases, and infections caused by the invaders, the

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Introduction
Every organism's body is being attacked and
invaded constantly by viruses and by living
organisms such as bacteria, protists, fungi, and
multicellular parasites. Without defenses against
the damage, diseases, and infections caused by
the invaders, the attacked organism would soon
die. Organisms have evolved myriad defensive
mechanisms to protect themselves from the
invaders vertebrates have evolved an extremely
sophisticated defense system called the immune
system, which is based on several types of highly
specialized white blood cells that search out and
destroy foreign materials that have entered the
host's body. Some of the cells even supply
long-term, future protection against reinvasion
by a previously defeated attacker. The
recognition of an invading substance (or
organism) by the immune system cells occurs at
the molecular level and is based on the
three-dimensional shapes of particular molecules.
The ability to recognize so many different types
of invaders is conferred upon the immune system
by a unique form of gene processing. A disease
such as AIDS, which destroys the immune system,
makes us realize with brutal clarity the
importance of the immune system-without it we
cannot live. We succumb to the hordes of
attackers.
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Types of immunity 1. Active immunity
production of antibodies by the organism
itself 2. Passive immunity acquisition of
antibodies that were produced by another
organism --mother to fetus via placenta
--from mothers colostrum (breast milk
produced late in pregnancy --injection
from antisera (antivenoms) 3. Natural
immunity immunity due to infection 4.
Artificial immunity due to inoculation with a
vaccine
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Function defends the body against foreign
invaders ANALOGY A castle First line of
defense Physical barriers EX Castle wall,
moat (This is our skin, mucous membranes)
Second line of defense Non-specific
defenses EX Mac the guard dog. He attacks
anything that doesnt belong. It could
be enemy soldiers, the mailman, the
newspaper carrier-anything that is not
part of the castle. He doesnt care. Hes
NOT specific in what he attacks. (This is
a group of cell called macrophages, an
inflammatory response, a fever, etc.)
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Third line of defense Specific defenses EX
Specially trained soldiers that identify
specific enemies and attack them
appropriately. T soldiers are trained in
hand-to-hand combat getting close to the
enemy. B soldiers are trained in attacking
at a distance, using weapons called
antibodies. (This consist of T cells and B
cells, which attack SPECIFIC foreign
particles.) To avoid not getting attacked, you
need to know the password. If you say the
password, you can get through all of the
above. In our bodies, the password is a set
of cell-surface markers (carbs., proteins) such
as the major histocompatability complex MHC.
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• Three cooperative lines of defense have evolved
  to counter unwanted intruders.
• --Two of these are nonspecific - that is, they do
  not distinguish one infectious agent from another.

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Major Components

• Leukocytes (White Blood Cells) Macrophages,
• T Cells, B cells
• Proteins Antibodies, Histamine
• Organs
• --Lymph nodes, spleen, tonsils filter
  foreign
• particles out of lymph contain WBCs that
  destroy
• foreign particles.
• --Bone marrow, thymus produce WBCs

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First line of defense
We need to get certain substances into our
bodies, such as food, water, and air. The
passages through which these substances pass
are obvious places in which microbes and other
foreign particles can enter our bodies. Thus,
we should have defenses through each of these
openings to prevent invasion by microbes.
Obviously, none of these defenses are perfect,
as we still get sick.
1. Skin that cannot normally be penetrated by
bacteria or viruses (minute abrasions may allow
their passage). 2. Mucous membranes that line
the digestive, respiratory, and genito/urinary
tracts bar the entry of potentially harmful
microbes.
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SKIN How skin prevents entry of pathogens
--Secretions from sebaceous and sweat glands give
the skin a pH ranging from 3 to 5, which is
acidic enough to prevent colonization by many
microbes. --Antimicrobial proteins found in
salivia/tears helps to keep bacterial growth in
check Bacteria on skin prevent other bacteria
from growing. Skin has several tough/keratinized
layers Lysozyme, is present on the skins
surface-- digests the cell walls of many
bacteria, destroying them.
MUCOUS sticky, traps bacteria, contains
phagocytes, produces lysozymes Cilia sweeps
mucous up to be swallowed to kill bacteria.
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Second line of defense (Nonspecific defenses, Mac
the guard dog) Clearly foreign
particles are able to slip past our first line
of defenses. We therefore need another type
of defense for when this happens. FIRST,
though, we need to know who is foreign, and who
is self. Distinguishing Self from Non-self
(Whats the password?) 1. All cells have
molecules sticking out of their membranes
(carbs, proteins of glycocalyx). --Immune cells
use these to distinguish between self cells
and non-self cells. 2. Major
Histocompatability Proteins (MHC) --One class
of of self labels
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MHCs cont.

• Bind to foreign particles and present them at
  the
• cells surface.
• ANALOGY Someone whos in a hostage situation
  may
• try to get near the window and hold up a sign
  saying
• Help! The bad guys in here!!! This is the
  same thing
• these proteins display portions of the the
  invader so
• that other immune cells know what to attack.
• MHC 1- found on every cell in the body
• MHC 2- found only on immune system cells

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Problems with MHCs
Organs and tissue donations? rejection by the
recipients immune system. SOLUTIONS 1. Try
to match self-markers between donor and
recipients (using relatives is a common
approach to doing this) 2. Use drugs that
suppress the immune system
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Second line of defense Defenses

• Phagocytic leucocytes (macrophages) (type of WBC)
• Chemical recognition of invader
• Moves toward the invader via amoeboid movement
• Ingest a microbe by endocytosis
• Enzymatic digestion (lysososmes)
• --Molecular pieces not digested are
  displayed
• on the membrane of the macrophage
• antigen presentation
• NON-SPECIFIC attack all antigens,
• indiscriminately

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• Inflammatory Response
• Localized response due to tissue damage by a
  physical injury or by the entry of
  microorganisms.
• Damaged cells or bacteria release chemical
  signals that cause nearby capillaries to dilate
  and become more permeable, leading to clot
  formation at the injury.
• Increased local blood supply leads to swelling,
  redness, and heat of inflammation.

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• 1. Histamine is released.
• --Triggers both dilation and increased
  permeability of nearby capillaries.
• --WBCs and damaged tissue cells also discharge
  prostaglandins and other substances that promote
  blood flow to the site of injury.

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2. Clotting elements delivered to the injured
area. --Clotting marks the beginning of the
repair process and helps block the
spread of microbes elsewhere. 3. Migration
of phagocytic cells from the blood into the
injured tissues. --Phagocyte migration usually
begins within an hour after injury.
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Third line of defense (Specific Defensestrained
soldiers)
Mac the guard dog does a decent job protecting
us, but if we know of a specific invader, we want
to deal with it immediately. We do this by
sending out soldiers to specifically search out
and destroy these invaders. This neutralizes the
threat much more effectively. So how does the
the body identify and destroy a specific type of
invader?

• Players
• 1. ANTIGEN molecule that causes antibodies
• ANTIBODIES proteins that circulate through the
  blood
• that help recognize antigens.
• --Made by lymphocytes and specific to one
  antigen.

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3. White Blood Cells (leucocytes) B lymphocytes
(cells) -- Only in limited supply since
WBCs make up only 1 of the total
number of cells in the bloodstream
--Body will clone(mitosis) the appropriate B cell
type antibody-secreting cells secrete
antibodies immediately and help fight off
the primary infection Memory Cells do
not secrete antibodies after the first
infection, but are long-lived and
circulate through the bloodstream waiting
for a secondary immune response to the pathogen
Helper T Cells chemically recognizes the
antigen being presented and become
activated. --Turns the immune response
from non-self to antigen-specific as the
identity of the antigen is determine
--Activates specific B cells
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Primary Immune Response Clonal selection
antigens activates specific immune
responses --Individual usually becomes sick
while this is occurring. Secondary Immune
Response Rapid division of memory cells
after a second exposure? stronger, more
rapid response --Vaccination injection of dead
or weakened virus or bacterium triggers
clonal selection and production of memory
cells if the real virus or bacteria ever
enters the body, these memory cells rapidly
proliferate and destroy it before the
individual gets sick.
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Humoral Immune Response (HIR)/Antibody production
Attacks bacteria, viruses, and toxins moving
freely through the blood this is like
attacking your enemy at a distance using
weapons called antibodies.

• Specific antigen is identified
• Specific B cell is identified producing an
  antibody that will bind to the antigen of the
  invader.
• 3. B cell clone themselves rapidly increasing the
  number of the
• same type of B cells.
• Antibody production kicks into high gear
  producing a lot of antibodies.
• Antibodies circulate in bloodstream finding the
  matching antigen.
• 6. Antibodies eliminate the pathogen

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Antibiotics chemicals that take advantage of the
differences between prokaryotic
(bacteria) cells and eukaryotic (our own)
cells. Block specific metabolic
pathways/destroy cell wall of the
bacteria. Viruses make use of our own body
cells metabolism to create new viruses
because they do not have metabolic
pathways --Host cell not affected by
antibiotics
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Diseases of the Immune System

• Allergies hypersensitive response to
  environmental
• antigens (allergens)
• EX Hay fever is an immune response to pollen?
• inflammatory response (sneezing,
  runny nose, teary
• eyes, smooth muscle contractions that
  lead to
• difficulty breathing)
• Solution antihistamines-drugs that help this
  by blocking
• histamine(protein that causes the
  inflammatory
• response
• EX Anaphylactic Shock severe reaction?abrupt
  dilation of blood vessels?loss of blood
  pressure?death (peanuts)
• Solution Epinephrine-contricts blood vessels
  and raises
• blood pressure again (Epi-pens)

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• Immunodeficiency
• EX SCID (Severe Combined Immunodeficiency
  Disorder)
• --Genetic condition resulting in failure of
  both branches
• of the immune system
• Bubble Boy His parents had a child
  that died of SCID, so this
• time, they decided to raise their child in
  a bubble if he had
• the disorder. He did. They raised him for
  14 yrs. But then he
• died during an attempt at a bone marrow
  transplant (the
• donor tissue had a virus). His whole life,
  he went without
• human touch.
• EX HIV (Human Immunodeficiency Virus)
• --Virus that attacks the immune cells
  (particularly T
• helper cells)
• --When T helper cells drops below a certain
  point, we
• call it AIDS (Acquired Immunodeficiency
  Syndrome)
• this usually takes 10 yrs.

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• Autoimmune disorder immune cells attack self
  cells
• --Not fully understood
• --Multiple sclerosis, Rheumatoid arthritis,
  Type I
• diabetes, Chrons disease