7375788
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Mind Map by George Patient, updated more than 1 year ago
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Cell Recognition and the Immune System
- Important definitions:
- A pathogen is an organism
that causes a disease
- An antigen is the protein shape on the
outside of a cell that stimulates an
immune response
- An antibody is a large
y-shaped protein molecule
that has a specific shape,
complimentary to that of
one particular antigen
- A pathogen is an organism
that causes a disease
- Cell identification
- All types of cells have
specific molecules on
their surface that can be
used to identify them
- This allows the immune
system to identify cells
as being self or non-self
- This allows the immune
system to identify cells
as being self or non-self
- All types of cells have
specific molecules on
their surface that can be
used to identify them
- Defence mechanisms:
- Non-specific mechanisms
- Primary defences (barriers to
pathogen entry)
- 1. The skin
- The cells of the
epidermis
- The cells of the
epidermis
- 2. Mucous membranes
- Goblet cells produce
sticky mucus which
traps pathogens
- Goblet cells produce
sticky mucus which
traps pathogens
- 3. HCl in the stomach
- This denatures
proteins/enzymes of pathogens
and kills them
- This denatures
proteins/enzymes of pathogens
and kills them
- 4. Tears in the eyes
- Contains lysozymes this
hydrolyses peptidoglycan in
bacterial cells
- Contains lysozymes this
hydrolyses peptidoglycan in
bacterial cells
- 5. Wax in ear canals
- Traps pathogens
- Traps pathogens
- 1. The skin
- Phagocytosis
- When physical barriers are breached
by pathogens the non-specific
immune response takes place
- Pathogens or infected body
cells release a chemical
alarm causing the dilation
of local blood vessels
causing the area to
become warm and red
- The permeability of the capillaries also
increases causing swelling
- This means
phagocytic white
blood cells move
to the area
- This means
phagocytic white
blood cells move
to the area
- The permeability of the capillaries also
increases causing swelling
- Pathogens or infected body
cells release a chemical
alarm causing the dilation
of local blood vessels
causing the area to
become warm and red
- REMEMBER
- 1. Phagocytes are attracted by
chemicals produced by pathogens
- 2. Phagocyte attaches to pathogen
- 3. It engulfs the pathogen to form vesicles called phagosomes
- 4. Lysosomes in phagocytes fuse with phagosomes
- 5. Hydrolytic enzymes released from lysosomes hydrolyse pathogens
- 6. Soluble products of digestion are absorbed into the cytoplasm of phagocytes
- 6. Soluble products of digestion are absorbed into the cytoplasm of phagocytes
- 5. Hydrolytic enzymes released from lysosomes hydrolyse pathogens
- 4. Lysosomes in phagocytes fuse with phagosomes
- 3. It engulfs the pathogen to form vesicles called phagosomes
- 2. Phagocyte attaches to pathogen
- 1. Phagocytes are attracted by
chemicals produced by pathogens
- When physical barriers are breached
by pathogens the non-specific
immune response takes place
- Primary defences (barriers to
pathogen entry)
- Specific Immune Response
- This is a response to detection of pathogens or antigens
that involves white blood cells called B lymphocytes and T
lymphocytes
- B cells and T cells
- B lymphocytes originate and mature in
the Bone marrow
- T lymphocytes originate in the bone
marrow and mature in the thymus
- B and T cells have
specialised receptor
molecules on their cell
surface membranes
- Each cell is capable of
recognising one specific shape
of antigen
- Each has different protein receptor molecules on
its surface complimentary to the shape of one
specific antigen
- There are not many lymphocytes
specific to one antigen
- There are not many lymphocytes
specific to one antigen
- Each has different protein receptor molecules on
its surface complimentary to the shape of one
specific antigen
- Each cell is capable of
recognising one specific shape
of antigen
- Clonal Selection is:
- The lymphocyte with complimentary protein
receptors to those of the pathogen/antigen
will be "selected" and stimulated to divide to
build up numbers to a level where they can be
effective in destroying the pathogen
- The lymphocyte with complimentary protein
receptors to those of the pathogen/antigen
will be "selected" and stimulated to divide to
build up numbers to a level where they can be
effective in destroying the pathogen
- B lymphocytes originate and mature in
the Bone marrow
- B cells and T cells
- Cell mediated immunity - T cells
- T cells respond to an organisms own
cells that have been infected by a
pathogen
- 1. Phagocytes and infected body cells place some
of the pathogen's antigens on their cell surface -
called antigen presentation
- 2. The helper T cells with the specific receptor for the
antigen come into contact with the infected cells and the
receptor on the T helper cells binds with the antigen, this is
the selection of the correct T lymphocyte
- 3. This stimulates the selected T cell to divide rapidly by mitosis
- 4. These cloned T helper cells will:
- Form T memory cells
- Stimulate phagocytosis
- Stimulate B cells to divide and produce antibodies
- Activate cytotoxic cells
- 5. Activated cytotoxic T cells kill infected
cells by producing a protein called perforin
that makes holes in the cell surface
membrane
- This makes the CSM permeable
and water and solutes enter/exit
freely
- Ideal for killing virus'
- This makes the CSM permeable
and water and solutes enter/exit
freely
- Form T memory cells
- 4. These cloned T helper cells will:
- 3. This stimulates the selected T cell to divide rapidly by mitosis
- 2. The helper T cells with the specific receptor for the
antigen come into contact with the infected cells and the
receptor on the T helper cells binds with the antigen, this is
the selection of the correct T lymphocyte
- T cells respond to an organisms own
cells that have been infected by a
pathogen
- Humoral Immunity - B cells
- B cells respond to infection by
producing antibodies, antibodies
are proteins that are soluble in
the blood and tissue fluid of the
body
- 1. An antigen enters the blood
- 2. There will be one B cell that has an antibody
on its surface whose shape fits the antigen, the
shapes of the antibody and antigen are
complementary
- 3. The specific B cells take in these antigens by
endocytosis and present them on the surface of the cell
- 4. Specific T helper cells attach and stimulate this
B cell to divide by mitosis to form a clone of B
cells that will produce antibodies to that specific
antigen
- This process is called clonal selection
- 5. B cells develop into:
- Plasma cells
- These cells secrete antibodies
into the blood plasma this is
the primary response
- These cells secrete antibodies
into the blood plasma this is
the primary response
- B memory cells
- These an enable an increased and more
rapid response to a second exposure to
infection (secondary response)
- These an enable an increased and more
rapid response to a second exposure to
infection (secondary response)
- Plasma cells
- This process is called clonal selection
- 4. Specific T helper cells attach and stimulate this
B cell to divide by mitosis to form a clone of B
cells that will produce antibodies to that specific
antigen
- 3. The specific B cells take in these antigens by
endocytosis and present them on the surface of the cell
- 2. There will be one B cell that has an antibody
on its surface whose shape fits the antigen, the
shapes of the antibody and antigen are
complementary
- B cells respond to infection by
producing antibodies, antibodies
are proteins that are soluble in
the blood and tissue fluid of the
body
- This is a response to detection of pathogens or antigens
that involves white blood cells called B lymphocytes and T
lymphocytes
- Non-specific mechanisms
- Multiplication of pathogens:
- Bacteria multiply by binary fission
- Virus multiplication:
- They enter the host cell and use the host
cell's DNA replication and protein
production to produce new viral particles
- They enter the host cell and use the host
cell's DNA replication and protein
production to produce new viral particles
- Bacteria multiply by binary fission
- Antibody structure
- Made up of:
- A constant region
- Four polypeptide chains (two
light two heavy) held together
by disulphide bridges
- A variable region, this has
a specific shape due to its
amino acid sequence.
- The shape of the variable region
and antigen are complementary to
each other, this is the antigen
binding site
- The shape of the variable region
and antigen are complementary to
each other, this is the antigen
binding site
- A hinge region that
enables antibodies
to attach to more
than one antigen
- A constant region
- 4 polypeptide bonds = quaternary structure
- Antigen binding site = tertiary structure
- Primary structure determines how polypeptide chains fold
- Primary structure determines how polypeptide chains fold
- Antigen binding site = tertiary structure
- Made up of:
- Agglutination
- Antibodies bind to antigens at
the ANTIGEN BINDING SITE at
the tip of the variable region
- This prepares pathogens for
destruction
- This prepares pathogens for
destruction
- Pathogens clump together (loads of
antibodies joining to pathogens which
join together) and can no longer attack
host cells
- The clumps are engulfed by phagocytic cells
- The clumps are engulfed by phagocytic cells
- Antibodies bind to antigens at
the ANTIGEN BINDING SITE at
the tip of the variable region
- Responses
- Primary Response:
- This is the first time the immune system
encounters a pathogen, the initial selection of
the correct B cell and subsequent cloning
take time as there is only one B cell specific to
the antigen
- Antibodies are
secreted into
the blood
- Antibodies attach to and
destroy pathogens and
any antigens they produce
- Individual plasma cells only survive
for a few days and memory cells
survive for a long time
- Individual plasma cells only survive
for a few days and memory cells
survive for a long time
- Antibodies attach to and
destroy pathogens and
any antigens they produce
- This is the first time the immune system
encounters a pathogen, the initial selection of
the correct B cell and subsequent cloning
take time as there is only one B cell specific to
the antigen
- Secondary response
- This is a much greater and quicker response
because of the memory cells
- This is because the memory cells
remaining in the cells increase the
chance of the B cells of the correct
type meeting the pathogen
- This is because the memory cells
remaining in the cells increase the
chance of the B cells of the correct
type meeting the pathogen
- This is a much greater and quicker response
because of the memory cells
- Primary Response:
- Vaccination
- Vaccination produces immunity to specific
diseases by exposing someone to antigenic
material that has been rendered harmless
- Active immunity
- This is produced by the stimulation of
antibodies and memory cells by the
body's immune system
- Natural active
immunity =
response by the
immune system to
infection
- Artificial active immunities =
response by the immune
system to vaccination
- This is produced by the stimulation of
antibodies and memory cells by the
body's immune system
- Passive immunity
- Produced when antibodies are
introduced from an outside source
- Antibodies are not replaced by the body
and no memory cells are produced
- Antibodies are not replaced by the body
and no memory cells are produced
- Maternal antibodies are passed to
foetus from the mother across the
placenta
- Anti-venom given to snake-bite victims
- Anti-venom given to snake-bite victims
- Produced when antibodies are
introduced from an outside source
- Herd immunity
- When a large proportion of the
population is vaccinated it is
hard for the pathogen to spread
- When a large proportion of the
population is vaccinated it is
hard for the pathogen to spread
- Ethics
- Development
involves animals
- Is it fair to make the
vaccine compulsory in
order to be effective?
- Should expensive vaccines
continue when a diseases is
nearly eradicated
- Development
involves animals
- Vaccination produces immunity to specific
diseases by exposing someone to antigenic
material that has been rendered harmless
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