Download (4) Adaptive Immune System and the Humoral Immune Response

Immune System Part IV:
The Adaptive Immune System and Humoral Immunity
Adaptive Immune System (Specific Immune System):
Humoral Immunity
Humoral Immunity
•
Selected B cells produce copious amounts of
antibodies that interact with antigens found
on pathogens.
•
Needs the support of helper T cells.
Adaptive Immune System: Humoral Immunity
• An antigen is any
material that
stimulates selected
B cells to produce
copious amounts of
antibodies.
• An epitope is the part of an
antigen to which the antibody
attaches. An antigen can have
more than one epitope or type of
epitope.
• Antigens include
bacterial cell walls,
viral parts, flagella,
etc.
Adaptive Immune System: Different Epitopes on
Different Antigens
Different epitopes found on different types
of antigens.
Humoral Immunity: Selecting B cells
• Naïve B cell receptors are
different for each B cell.
• Antigens attach to a receptor site
on the B cell.
• Antigens are brought into the
cytoplasm of the B cell.
• Antigens attach to MHC II
proteins and are transported to
the cell membrane.
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Humoral Immunity:
Cloning Selected B cells
• An activated helper T
cell makes a match
with MHC II/AG
complex.
•
Helper T cell secretes
cytokines which causes
the B cell to reproduce
and making plasma B
cells and memory B
cells.
Humoral Immunity:
Cloning Selected B cells
• For this particular
selected B cell,
thousands of B plasma
cells are cloned. They
are identical to the
original B cell.
•
Each plasma B cell can
synthesize 2,000
identical AB per
second.
This illustrates how out
of thousands of different
naïve B cells, only the
one with the correct
receptor site is selected
and cloned.
Antibodies Can Inactivate Antigens
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Opsonization and Inactivating an Antigen
Opsonization: Certain bacterial cells have so many AG determinants
that the antibodies coat the bacteria cell. The constant regions stick
out (called the FC region). The phagocytes have FC receptors. This
interaction allows the phagocyte to roll over the pathogen and
phagocytosis occurs.
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Activation of B-Cells
Another drawing of B cell selection and activation of
plasma cells.
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Homeostasis: Halting the Attack
•
Regulatory T cells (Treg) help to halt the
immune response.
•
Do not know how they are activated; possibly
through antigens.
•
Thought to stop any further naïve B or T cells
from being activated. The immune response
then stops because activated immune cells die
due to their short life span.
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Secondary Immune Response
• Memory B cells and T cells are selected for
when exposure to a subsequent pathogen occurs
and the memory cells are a match for the antigen.
• Memory B cells and T cells quickly reproduce,
making plasma B cells, helper T cells and
cytotoxic T cells (effector cells).
• Plasma B cells begin to make AB and cytotoxic
T cells begin to destroy infected cells.
Secondary Immune Response
Preventing Disease with Vaccines
Immunity-Subsequent exposures to pathogens do not
result in the disease. Active immunity causes memory B
and T cells to be made. Passive immunity results from
obtaining pre-made antibodies with no memory cells being
made.
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Type of Immunity
Natural active immunity- (ex. mumps) organism is exposed
to the actual pathogen and gets the disease. Memory cells are
made. Subsequent exposure to the pathogen does not cause
the disease.
Artificial active immunity- (vaccine) person is given inactive
parts of the pathogen so that memory cells are made.
Exposure to the pathogen does not cause the disease.
Natural passive immunity- AB in breast milk and the
antibodies of a pregnant woman cross the placenta to her
fetus. Lasts a few weeks to a few months. No memory cells
made. Can succumb to the disease later.
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Artificial Passive Immunity
Artificial passive immunity- Patients exposed to a
serious pathogen maybe given a shot with preformed AB against the disease.
The AB are found in the
plasma of a person who
has had the disease. The
plasma is processed so
that all the blood clotting
proteins are removed
forming serum.
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When the Innate Immune System Goes Awry
• Certain bacterial infection
can induce an overwhelming
inflammatory response.
• Too many mast cells and
phagocytes release huge
cytokines and histamines.
Too much fluid leaks from
the capillary bed into the
tissues. Blood pressure drops
dangerously low and the
tissues swells. Can be fatal.
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When the Adaptive Immune System Goes Awry
• Not all self-reactive
lymphocytes are destroyed
in development. Those
that survive are
suppressed.
• Autoimmune diseases
happen when certain
suppressed lymphocytes
are activated and attack
the body’s own tissue.
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A,B,O and AB Blood Groups and the Immune
System
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Antibodies and the Rh Factor
The HIV Virus and Immunity
• This is the HIV retro virus that causes AIDS. It
contains RNA.
• During replication, the
RNA is transcribed to
DNA. This process
does not correct for
transcription errors.
This virus easily
mutates.
HIV Replication
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Progress of AIDS
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Helper T Cell and HIV virus
A T-cell being
infected by the
HIV virus
(blue particles)
Created by:
Carol Leibl
Science Content Director
National Math and Science