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UNIT IMMUNE RESPONSE:
Specific and Nonspecific Body
Defenses
The host-parasite relationship may
result in an episode of disease.
In this case, the body will mount two
general forms of defenses: nonspecific
defenses and specific defense centered
In the Immune system.
THE FATE OF INFECTING
ORGANISMS:
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Several possible fates await organisms that
cause infections.
This is a matter of practical interest, because
the transmission of the diseases to other
individuals depends upon the escape of the
organisms from the
infected one.
1.
Some are destroyed by host tissue.
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Infections are not accomplished without resistance
on the part of the host because the host-parasite
relationship Isn 't a natural one.
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Fortunately, the capacity of hosts to destroy
parasites is so great that the great majority of
foreign living agents which manage to reach
living tissues and fluids, of the body are rapidly and
completely destroyed...ongoing all time, (exception:
Trypanosoma pg 302 add)
2. Some are eliminated in the
secretion and excretion of the host.
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Elimination in this manner varies with the
disease.
The longer the organism lasts, the more likely
the host is to eliminate large numbers of
numbers of infected agents.
Elimination can be through: pus, abscess ,
bursts, droplet in cough or sneeze,
feces
3.
If the disease proves fatal to host, many of the
infecting organisms are destroyed with the body.

Death of the host form the infection always
traps a large number of the infecting
organisms.
4. In some instances the organisms and the host
reach an impasse,

Where:
the organism is unable to cause serious
damage to the host, and yet the host is unable
to eliminate the organism...can occur
throughout the organisms life span. Ex
tuberculosis, typhoid fever
NONSPECIFIC MECHANISMS OF
DEFENSE:

The objectives of these mechanisms are to
prevent microorganisms from gaining a
foothold in the body and to destroy them if
they penetrate to the deeper tissues.
1.
Mechanical barrier: first line of defense for
the body, and are normally part of the body's anatomy
and physiology.
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a. skin: outermost layer of skin consist of
compacted, cemented cells
impregnated with the insoluble protein keratin
b. mucous membranes: line urinary, respiratory,
and digestive tracts
c. nasal hairs: trap particles in the respiratory
tract.
d. cilia: on the cells sweep and trap particles in
respiratory tract, and
coughing ejects the material.
2. Chemical defenses

The secretions and lubricating glands such
as the tears and saliva which contain the
enzyme lysozyme (breaks down
peptidoglycan cell wall of gram positive
bacteria)
3. Genetic barrier:

hereditary characteristics. Ex humans do not
suffer canine distemper because humans lack
the appropriate receptor sites for the virus
that causes the disease.
4. Inflammation:
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Nonspecific response to any trauma occurring
to tissues.
Includes: heat, swelling, redness and pain.
In some types of inflammation, phagocytes
accumulate in the whitish mass of cells,
bacteria, and debris called pus
5. FEVER

Is initiated by circulating substances called
pyrogens, which affect the brain's
hypothalamus and cause the hypothalamus to
raise the temperature. ..is believed to retard
the growth of temperature sensitive
microorganisms.
6. Phagocytes

engulf and destroy the microorganism of
disease. Ex neutrophils and monocytes
7. Complement system
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a series of proteins that circulate in the blood
and encourage phagocytosis.
Many immune reactions stimulate this
system to go into action.
SPECIFIC DEFENSES: (THE
IMMUNE SYSTEM)
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Center around the immune system
The immune system enables the body to
recognize a foreign agent as nonself, which is
something other than a person's own
substances (self).
The immune system takes a specific action for
neutralizing, killing, and eliminating that
agent.
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These actions involve nonspecific resistance as well.
On occasion, the immune system activity may lead to
tissue damage as seen in allergic disorders and
hypersensitivities.
The system is based on its ability to distinguish
characteristic proteins or protein-linked components
associated with alien substances.
There are 2 main branches of the
immune system:
1.
2.
. Antibody-mediated immunity (humoral
immunity)
Cell-mediated immunity
ANTIBODY-MEDIATED (HUMORAL)
IMMUNITY (AMI):
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Involves antibodies that are found in the blood
plasma and lymph.
Antibodies are produced by B cells in response to a
specific antigen.
Antibodies primarily defend as against bacteria,
viruses, and toxins in body fluids.
On exposure to antigenic determinants in lymphatic
organs, B-lymphocytes are activated and
differentiated to form plasma cells.
Plasma cells are specialized, differentiated cells that
synthesize and secrete antibodies specific for an
antigen.
CELL-MEDIATED IMMUNITY
(CMI):
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Depends on T cells and does not involve
antibody production.
Primarily a response to intracellular viruses,
multicellular parasites, transplanted tissue,
and cancer cells.
ANTIGENS AND ANTIBODIES:
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Antigen: a chemical substance that causes the body to
produce specific antibodies which the antigen can then
combine with.
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As a rule, antigens are foreign substances, not part of the
body's chemistry (most are proteins)
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Antibody: a protein produced by Blymphocytes in response to the presence of an
antigen and is capable of combining
specifically with the antigen (antibodies have
at least 2 antigen-binding sites)
Antibodies react with antigens to form
antigen-antibody complexes,which neutralize
toxins, inactivate viruses or lyse cells.
ANTIGENS:
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Immune responses are directed at a series of foreign
substances known as antigens, also referred to as
immunosens.
Most antigens are high molecular weight substances,
but low molecular weight substances (called hapten)
will also act as antigens if they bind to proteins in
the body.
The uptake and processing of antigens by
macrophages in the tissue is an initial, critical step
in most immune responses.
TYPES OF ANTIGENS:
Certain types of antigens are distinctive:
a.
b.
c.
Autoantisens: are a person's own self
antigens.
Alloantisens: antigens found in different
members of the same species. Ex RBCs
antigens A and B
Heterophile antisnes: identical antigens
found in the cells of different species.
d.
e.
f.
g.
Somatic antigens: antigens found on the
body cell
Capsular antigens: antigens in the bacterial
capsule
Flagellar antigens: found on an organisms
flasella
Exotoxins: protein substances that are also
antigens.
CLASSES OF
ANTIBODIES:
Are produced by the plasma cells.
=> Five classes:
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1. IgM: major component of the primary antibody
response in adult humans and is the first antibody to
appear in the immune reaction. It cannot diffuse
through cell membranes and is found almost
exclusively in the blood.
IgG: most common in the bloodstream and is found
in many secretions, such as spinal, synovial, lymph
fluids, provides natural type of passive immunity.
IgD: extemely small quantities in the serum. Found
at the surface of -lymphocytes and believed to be an
antigen receptor at this location.
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IgE: Occurs in minute concentrations in the
serum and is important in hypersensitivity
reactions, especially anaphylatic reactions
IgA: found in external secretions such as
those at the mucosal surfaces of the
respiratory, gastrointestinal, and urogenital
tracts. Is present in saliva, bile and urine and
is transferred in breast milk.
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The reaction of antibodies with antigens helps
neutralize the antigen and restrict the spread of
infection.
Certain antibodies react with the bacterial surface,
while others react with the flagella, pili, or capsules.
These reactions encourage phagocytosis.
When antibodies react with a virus, the viruses
cannot attach to the host cells and replicate.
CELLS OF THE IMMUNE SYSTEM:
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Lymphocytes of the lymphatic system are
derived from stem cells of the bone marrow.
These undifferentiated precursors cells
proliferate throughout life and replenish the
mature cells of the immune system.
TYPES OF IMMUNITY:
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An individual's genetically predetermined resistance
to certain diseases is called innate resistance.
Individual resistance is affected by sex, age,
nutritional status, and general health.
An individual may develop or acquire immunity after
birth.
Immunity is the ability of the body to specifically
counteract foreign organisms or substances.
=> TYPES
a.
b.
c.
Acquired immunity is specific resistance to
infection developed during the life of the
individual. Results from the production of
antibodies.
Naturally Acquired Active Immunity: results
from infection and may be long lasting.
Naturally Acquired Passive Immunity:
antibodies transferred from mother to fetus.
Lasts up to a few months
Naturally acquired Active immunity