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THE IMMUNE RESPONSE
BIO11
This lesson meets the following DoE Specific Curriculum Outcomes for Biology 11: 116-7
THE IMMUNE RESPONSE
• The first line of defense: Skin and
mucous membranes provide physical
barriers that prevent most infectious
organisms from entering the body.
• The second line of defense: nonspecific immune response by
macrophages (a type of leukocyte)
destroy microbes by phagocytosis and
inflammatory response.
MACROPHAGES
•
Two responsibilities:
1. They release a chemical that causes
blood vessels to dilate, increasing
blood flow and temperature at the site
of the infection. The heightened temp
may be enough to destroy the invader.
2. They seek out and destroy foreign
invaders through phagocytosis. The
antigens of the invader are not
destroyed but are pushed toward the
cell membrane of the macrophage.
IMMUNE RESPONSE cont.
• The third line of defense: The specific
immune system. This includes a variety
of cells that recognize foreign
substances and act to neutralize or
destroy them. Lymphocytes are the
primary components of this system.
LYMPHOCYTES
• Cells hat produce antibodies (proteins
that protect the body from invaders by
reacting with the antigens on the
invader’s cell membrane).
• Our immune system has two different
types of lymphocytes: T cells and B
cells.
T CELLS
• Produced in the bone marrow and stored
in the thymus gland.
• These cells act as sentries or guards for
the immune system - its mission is to
seek out the intruder and signal the
attack.
• Some T cells identify the invader by its
antigen markers. Once the antigen is
identified, another T cell passes this
information on to the antibodyproducing B cell.
B CELLS
• Both produced and
mature in the bone
marrow.
• These cells are
responsible for the
production of
antibodies and
memory cells.
HELPER T CELLS
• Circulate in the blood plasma looking for
the antigens of foreign invaders that have
been engulfed by macrophages.
• Once an invader is detected, the helper T
cell sends a chemical message to the B cell
which produces the appropriate antibody.
ANTIBODY RESPOSE
• The antibody is released into the body
to search for the invader. Once found,
the antibody attaches itself to the
invader’s antigen, thereby disabling
invaders.
• The antigen-antibody complex is then
engulfed and destroyed by a
macrophage.
KILLER T CELLS
• Helper T cells also activate an
additional defender, the killer T cells,
which search for intruders and disable
it by puncturing its cell membrane.
• The true value of these cells is seen
with viruses, which hide within a
familiar host cell. The killer T cell
attacks the infected cell, preventing the
virus from reproducing.
SUPPRESSOR T CELLS
• Once the entire battle with the foreign
invader has been won, these cells signal
the immune system to shut down.
• Helper T cells and memory B cells, made
by the B cells, remain in the blood,
ready to trigger another immune
response if the body is infected with the
same pathogen.
ACTIVE VS. PASSIVE
•
Immunity can be provided in two ways:
1. Passive immunity: memory cells are
made to recognize a previous infection
or when an individual receives
antibodies from another person to
combat disease (during pregnancy).
2. Active immunity: done through medical
intervention and vaccines that may be
induced in healthy people so that they
can avoid becoming ill later (flu
vaccine).
PASSIVE IMMUNITY DURING
PREGNANCY
• Antibodies from the mother’s system
cross the placental barrier during
pregnancy and during breast feeding.
• This give the newborn short-term
immunity to some diseases.