UNIT THREE
BIOLOGY
AREA OF STUDY #2: DETECTING &
RESPONDING
EXAM REVISION LECTURE
CHP 8: DEFENSE AGAINST DISEASE
CHP 8 TOPIC.1: The Lymphatic System
Function:
1. take up excess tissue fluid and return it to the bloodstream (drained
from thoracic duct into major veins)
2. absorb fats at the intestinal villi and transport to the circulatory
system (90% of digested fat is absorbed this way)
3. defend against disease
CHP 8 TOPIC 1: The Lymphatic System
• key component of the immune system
• blind ended open system, similar in structure
to veins, arteries and capillaries
• returns proteins that leak out of capillaries
back into blood circulaltory system
• White blood cells (leucocytes) move around in
the circulatory and lymphatic system seeking
foreign and damaged cells
• lymphocytes (immune cells in the lymph
nodes) are produced by primary lymphoid
organs bone marrow, thymus)
• immune responses cause swelling in
secondary lymphoid organs (lymphoid nodes,
spleen, tonsils, adenoids).
CHP 8 TOPIC 1: The Lymphatic System
Chapter 8 - Defence Against Disease
4
CHP 8 TOPIC 1: The Lymphatic System
Leukocytes, we will come back to these in more detail!
LEUKOCYTES
All produced in the Bone Marrow from Stem Cells
Granular Leukocytes
Agranular Leukocytes
Have large, lobbed nuclei and distinctive granules in their
cytoplasm
Cytoplasm usually lacks granules and the
nucleus is more rounded
Neutrophils
Eosinophils
Basophils
Lymphocytes
•Most numerous WBC
•Main phagocytotic
cell
•Ingest bacteria and
phagocytize dead cells
• short lived
•Produce enzymes
which detoxify
foreign proteins and
fight parasatistic
infection
•Produce and release
heparin
(anticoagulant) and
histamine in response
to injury or infection
(T and B)
•Some produce
antibodies (B Cells)
and others attack
invading cells directly
(T Cells)
Monocytes/
Macrophages
•Largest WBC
• monocytes grow
into macrophages
•Phagocytotic cells
that don’t usually die
after consuming
pathogen
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Topic CHP 8.1 Questions:
1. Lymph vessels are open/ closed
2. Name two roles of the lymphatic system: _____________________, ________________,
_______________________________
3. Immune responses cause swelling in the _________________ ________________ organs
4. WBC are also known as: _________________
5. Granular Leucocytes include: ____________________, _________________,
________________
6. Agranular Leucocytes include T and B cells as well as: ________________________
CHP 8 TOPIC 2: THREE LINES OF DEFENCE
Immune System: Consists of Three Lines of Defence
Pathogen invades Tissue/ Cell
Non Specific Defence
Barriers
Physiological
Chemical
Mechanisms
Phagocytes
and
NK Cells
Mechanisms
Specific Defence
Inflammation
Basophils
Mast Cells and
platelets
Histamines &
phagocytosis
B Cells
T Cells
Memory Cells
Antibodies
1
Humoral Immunity
2
Chapter 8 - Defence Against Disease
Cell Mediated
Immunity
3
7
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Non-specific mechanisms:
Physical and Barriers: 1st line of defence
8
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Physical Barriers
Chemical Barriers
•
•
Animals
– Skin (dry, hard keratin)
– mucous secretions on membranes
– Ciliated membranes (throat and lungs)
– Lysosomes
– Gastric acids
– External hairs
•
Plants
– Waxy cuticle
– Cell wall
– Plasma membrane
– External hairs
•
Animals
– Interferons (triggered by pathogenic
double stranded RNA not found in
unaffected cells)
– (other) cytokins (protein messengers)
that can cause apoptosis and attract
WBCs
– Lactic acid
– Lysozyme, an enzyme, intears, sweat,
salica
– Natural flora
– Complement proteins
Plants
– Secondary substances: antibiotics,
proteases, cellulases and chitinases
– Hormone ecdysone (causes insects to
moult
9
– toxins
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Skin
• An intact skin acts as a barrier against entry by micro-organisms. A cut or
abrasion will allow entry of bacteria or viruses.
– Hardening of outer layers
• Provides a physical barrier
– Anti-bacterial and anti-fungal secretions
• Produced by sweat glands, sebaceous (oil) glands, bacterial flora of
the skin
– Lack of moisture
• Limits growth of microorganisms
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Mucous Membranes
• secreted by the cells lining your respiratory tract
•
traps bacteria which are then swept upwards to the back of the throat by
the action of cilia.
• some of the mucus and bacteria is then swallowed, coughed or sneezed
out, or blown out through the nose.
• promote growth of natural flora whose secretions limit pathogen growth
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CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Natural Secretions
• Many secretions of the body contain bactericidal agents. Tears and
saliva contain lysozyme, an enzyme that cause bacteria to lyse or
burst. Acid in the stomach also kills many bacteria.
Peristalsis
 Diarrhoea eliminates pathogens by movement towards the anus for
elimination
 Vomiting also results in removal of pathogens from body
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Enzymes
– Lysozyme in tears, saliva, sweat, nasal secretions and tissue
fluids breaks up (lyses) the cell wall of certain bacteria
Natural Flora
• Many different bacteria are normally found on the skin, gut and in
the vagina. These bacteria are harmless to the body and occur
naturally.
• The presence of these bacteria can inhibit the growth of pathogenic
bacteria as they compete for nutrients and space.
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CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Gastro-intestinal secretions
– HCl in stomach, alkaline fluids e.g. bile in duodenum
• Are of a pH which is outside the range of tolerance for many
microorganisms
• Many pathogens killed by stomach acids
Hairs and cilia
– Filter inhaled air
– Remove micro-organisms and other antigenic material (e.g.
pollen)
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Topic CHP 8.3 Questions:
1. List two physical barriers to infection in:
a)
b)
Plants: ______________________________, ________________________
Animals: _____________________________, _______________________
2. List two chemical barriers to infection in:
a)
b)
Plants: ______________________________, ________________________
Animals: _____________________________, _______________________
3. The hard surface of skin is a result of the protein called: _____________________
4. The first layer of skin is called the : ____________________
5. Tears and sailva contain ________________a bacterial agent
CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
Non-specific mechanisms:
Non-Specific Cellular Defences:
2nd line of defence
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CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
Non Specific Defence
PHYSIOLOGICAL
CHEMICAL
Macrophages (big phagocytes) release
chemicals (INTERLEUKIN-1) which reset the
body’s thermostat in the hypothalamus,
allowing temperature to rise
INTERFERONS are a group of antiviral
chemicals, produced by some cells which
have been infected with viruses
COMPLEMENT PROTEINS there are 20
complement proteins present in body fluids.
They may be activated to fight infection:
Directly by the presence of pathogens, or
When antigens and antibodies combine (see
specific immunity
Action
High temp. helps as it:
• kills some pathogens
• increases the activity of some
lymphocytes and phagocytes
• speeds up the death of virus
infected cells
They can fight infection by:
• interfering with virus replication
• making unaffected cells more resistant
to viruses
• stimulating macrophages to destroy
virus infected cells
Activated complement proteins may:
• lyse (dissolve) pathogen cell walls
• coat pathogens, making them easier for
phagocytes to ingest
• attract leukocytes to site of infection
• stimulate the release of histamine
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CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
CELLULAR …
Monocytes
•
•
Largest of the white blood cells
become macrophages when they leave the bloodstream
Macrophages
•
•
•
gather in various tissues such as the lungs, liver, kidneys and brain.
are particularly active against micro-organisms that can live inside the cells of the person they
infect.
engulf bacterium
Neutrophils
•
•
•
•
•
•
The most numerous of the phagocytotic cells
Granulated nucleus
Attacks bacteria
Die after engulfing bacterial pathogen
Their dead cells become the bulk of
‘pus’ at wounds
CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
Eosinophils
• can be phagocytotic.
• secrete enzymes to kill parasitic worms among other pathogens
CHP 8 TOPIC 8.4: NON-SPECIFIC IMMUNITY – 2nd LINE
Basophil
- contain granules of toxic chemicals that can digest foreign
microorganisms. These are cells involved in an allergic response
Basophils are a type of white blood cell
(leukocyte). These cells help you fight
infections by releasing histamine and
other chemicals like heparin
(antocoagulant)
Mast Cells
- similar to basophils, mast cells contain a variety of
inflammatory chemicals including histamine and
seratonin. Cause blood vessels near wound to dilate! and
increase permeability of the capillaries
CHP 8 TOPIC 8.4: NON-SPECIFIC IMMUNITY – 2nd LINE
Natural killer cells (NK cells)
•
are a type of lymphocyte (like macrophages)
•
police the body in blood and lymph
•
lyse and kill cancer cells and virus-infected cells
•
act against any such target (i.e. non-specific)
•
recognise certain sugars on invader’s surface
•
are not phagocytic: attack membrane of target cell and cause it, and its nucleus, to
disintegrate
CHP 8 TOPIC 8.4: NON-SPECIFIC IMMUNITY – 2nd LINE
Platelets
• cell fragments circulating in blood
• also release histamine and involved in clotting of
blood
CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
Non Specific Defence
C
E
L
L
U
L
A
R
P
H
A
G
O
C
Y
T
E
S
Macrophages/ Monocytes:
• largest WBC
• monocytes grow into macrophages
Neutrophils:
• most numerous WBC
• main phagocytotic cell
• ingest bacteria and phagocytize dead cells
Action
Phagocytes engulf, ingest, digest and
destroy invading pathogens, damaged
cells and debris. They can destroy up to
100 bacteria before dying themselves
Eosinophils:
• can be phagocytotic.
• secrete enzymes to kill parasitic worms among other
pathogens
Natural Killer (NK) Cells
A type of lymphocyte which provide some protection from
viruses and cancer
They can destroy cells which have been
infected with viruses. They can also
destroy some cancer cells.
Mast Cells
Large cells in connective tissue filled with granules. Important
inflammatory response
They release histamine in response to
injury and in allergic reactions:
histamines cause: dilation/ increased
permeability (blood. Vessels)
Basophils
Granular leukocytes present in blood. Important in inflammatory
response
Release histamine and seratonin
Platelets cell fragments circulating in blood
Also release histamine and involved in
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clotting of blood
Topic CHP 8.4Questions: 2nd Line of Defence
FEATURE
PRODUCED/
FOUND
FUNCTION
KEY FEATURES
Leokocyte
Monocytes
Macrophages
Neutrophils
Basophils
Eosinophils
Nk Cells
Mast Cells
Stem Cells
Interferons
Compliment Proteins
Vasodilation
Inflammation
Fever
Interleukin-1
Prostaglandins
Pyrexia
-
Cytokines
Histamines
Seratonin
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
Blood vessels
dilate
Increased
blood flow to
region
Redness
Capillaries
become
permeable and
leaky
Edema
Heat
Mast Cells
Pathogens
Enter Tissues
Basophils
Produce
Histamine and
seratonin etc
Platelets
Complement
Proteins
Pus
Phagocytes
move to an
area
Increased
phagocytosis
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
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CHP 8 TOPIC 5: FEVER - PYREXIA
The Cause of Fever
28
Topic CHP 8.5Questions:
1. True/ False: mast cells are only found in muscle cells
2. True/ False: mast cells produce histamines and seratonin
3. True/ False: platelets produce histamines
4. True/ False: phagocytes will attack any pathogens that are identified as ‘non self’
5. True/ False: Edema is a build up of fluid within the circulatory system
6. What is the role of interleukin in the immune response:
________________________________________________________________________
Once a pathogen or other foreign material has entered the body, it is
not only bombarded with your non-specific defences but is
subject to attack by cells of immune system, the T and B
Lymphocytes.
This system is slower to take action but is more specific in its attack.
Specific Immunity
3nd Line of defence
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CHP 8 TOPIC 6: SPECIFIC IMMUNITY -INTRODUCTION
31
CHP 8 TOPIC 6: SPECIFIC IMMUNITY -INTRODUCTION
STEM CELLS
Bone Marrow- specialise into blood cells
NK Cells
(see non-specific defences)
Lymphocytes
Develop in bone marrow
Mature B Cells
(see non-specific defences)
Thymus processing
Mature T Cells
(see non-specific defences)
Migrate to Lymph nodes
Memory T Cells
Helper T Cells
Cytotoxic T
Cells
Migrate to Lymph nodes
Memory B
Cells
Plamsa B32Cells
Topic CHP 8.6Questions:
1. Stem cells produce a variety of cells including erythrocytes and leucocytes: give 5 examples
of cells that differentiate from stem cells:
– _________________________
1. _________________________
2. _________________________
3. _________________________
4. _________________________
5. _________________________
2. Where do B cells mature? ____________
3. What kind of cells produce antibodies: _________________
•
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
How Does The Body Know What Cells To Attack
Self and Non-self
all cells have marker proteins on their plasma membrane
•
these proteins are the products of the MHC genes. each person has different
MHC genes (like a fingerprint).
•
therefore marker proteins are specific to each person/organism
•
cells with the body's own marker proteins are accepted as “self”. these proteins
are not antigenic to our own immune system.
•
cells with foreign markers are recognised as “non-self”. these marker proteins
are antigenic for us.
•
antigen receptors are also known as immunoglobulins (Ig)
•
It is the binding of receptor (immunoglobulin and antigen that initiates an
immune response
•
class 1 markers found on all cells except rbc. class 2 – only on b, t cellsand some
macrophages
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Antigens
•
the term “antigen” originates from “antibody generator” – triggers immune response
•
defined as a substance that, when it invades the body, will stimulate the formation of a specific
type of antibody
•
usually protein or polysaccharide
•
may be free e.g. in the bloodstream, or attached to the cell surface of a pathogen
•
critical in differentiating “self” and “non-self”
•
self antigens on the cell membranes are called “markers”.
•
those markers critical to the success of transplantation form the mhc (major histocompatability
complex)
•
an antigen is typically a large complex molecule, not normally present in the body, that is capable
of producing an immune response
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Self Tolerance
•
Tolerance by the body's immune system to its own cells and tissues
•
During development (maturation), body removes any cells immune cells that attack ‘self’
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Blood Groups – Blood Antigens
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Rhesus Incompatibility
• A red blood cell antigen, the rhesus factor is present on the red blood cells
of a majority of people. Such people are rhesus positive (RH+). If the
antigen is absent a person is rhesus negative (Rh-). If a person who is Rhand comes into contact with RH+ blood will respond by producing
antibodies against the antigen. This can become critical in pregnancy
40
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Rhesus
Incompatibility
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Autoimmune Diseases
• these occur when the immune system loses its
ability to tolerate “self” antigens.
• the body produces “autoantibodies” and
sensitised T cells that attack the body’s
tissues.
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
The most common autoimmune diseases
– Multiple sclerosis: destroys the myelin sheath of the brain and
spinal cord.
– Myasthenia gravis: which impairs the communication between
nerves and the skeletal muscles
– Graves disease: the thyroid gland produces excessive amounts
of thyroxine
– Juvenile (type 1) diabetes mellitus: destroys pancreatic beta
cells, resulting in deficient insulin production
– Systematic lupus erythematosus, SLE : occurs in young females
and affects the heart, kidneys, lungs and skin
– Glomerulonephritis: a severe impairment of kidney function
– Rheumatoid arthritis: which systematically destroys joints
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Organ Transplants and Rejection
• Transplantation has mixed success because the immune
system is ever vigilant.
• There are four types of grafts
– Autografts: tissue grafts from one site to another in the
same person
– Isografts: tissue grafts from a genetically identical
individual (an identical twin)
– Allografts: tissue grafts from an unrelated person
– Xenografts: tissue grafts from a different animal species
e.g. pig or baboon.
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Organ Transplants and Rejection
• Autografts and isografts are ideal donor organs, and are
almost always successful, given
• Adequate blood supply
• No infection
• Xenografts are never successful.
• Allografts are most commonly used.
• ABO and other blood group antigens must match
• Cell membrane antigens are typed, and at least a 75% match is
needed to attempt a graft
• After surgery the patient receives immunosuppressive therapy
• Explosive bacterial and viral infection is the most frequent cause of
death in these patients, since the immune system is compromised
CHP 8 TOPIC 9 B & T CELLS – SOLDIERS IN ARMS
B & T Cells: A partnership
SPECIFIC IMMUNITY
Cell Mediated Immunity – T Cells
Humoral Immunity- B Cells
(Antibody Mediated)
antigen
B Cell
receptor (immunoglobuln)
binds with antigen
CLONAL SELECTION
T Helper Cell
binds with b cell
Releases chemicals to
attract phagocytes
T Cells
B Memory Cells
B Plasma Cells
T Memory Cells
Cytotoxic T Cells
Topic CHP 8.8Questions:
1. MHC = _________________________________________
2. What kind of cells have Ig on their surface: ________________ & ____________
3. Class 2 MHC markers are found on what kind of cells: ________________________
4. An antigen is: _____________________________________________________________
_________________________________________________________________________
5. A person with blood group A+ can donate blood to people with blood groups: ___________
& ____________
6. A person with Blood group O + can receive blood from: _________________________
7. B Cell proliferation is initiated by the presence of what two factors: ___________________
& __________________________
8. Killer T cells are part of ______________ mediated response
CHP 8 TOPICS 10 & 11: HUMORAL (Antibody mediated) IMMUNITY
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Antibodies- “immunoglobulins”
• B-cells have immunoglobulins on their surfaces.
• Immunoglobulins are proteins that identify antigens, (are antigen
receptors).
• Immunoglobulins are called antibodies when released from B Cells .
• The immunoglobulins of each B-cell have a specific structure and
recognise only one kind of antigen.
• There are millions of antigens that the body must be able to respond. In
response to this millions of different B-cells are produced with different
immunoglobulins on their surfaces.
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CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
The Structure of Antibodies
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Action of Antibodies
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Action of Antibodies
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Antibodies in summary …
Topic CHP 8.10 Questions:
1. True/ False: B and T cells produce immunoglubulins
2. Draw an antibody in the space below labelling: heavy chain(s), light chain(s), variable region
3. True/ False: Antibodies are long lasting molecules
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
•
immunoglobulins – Ig for short
•
When on the surface of a Lymphocyte – they are receptor sites. Off, they are antibodies!
•
both T and B cells have immunoglobulins on their surface
•
secreted immunoglobulins are called antibodies
•
it is the binding of antigen to receptor which triggers the specific immune response
•
during maturation, the genes that determine Ig structure are continually being rearranged. this
leads to new combinations of shape and charge in the antigen binding site
•
antibodies can combine with two antigens at once. this can cause clumping, or agglutination
•
the antigen – antibody complex promotes phagocytosis
•
activates complement proteins
•
neutralizes the binding site of an antigen
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CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
Clonal selection Theory
When an antigen enters the body it probably passes many B cells before it
meets one with the immunoglobulan with which it can combine. In effect
the antigen ‘selects’ the B cell that will lead to its death
•
Antigen ‘selects’ B Cell and its immunoglobulan
•
B cell rapidly reproduces (mitosis) to produce identical daughter cells
•
Each of these reproduces rapidly to produce a large clone of cells
•
Cell cloned in this way will have exactly the same DNA and antibodies
•
Most will differentiate into in plasma B cells, others into memory cells
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
B Cells & theHumoral (Antibody Mediated) Immunity
•
B Cells provide - Humoral (Antibody Mediated) Immunity
•
they can produce large quantities of antibodies in response to a foreign
antigen
•
Must recognise ‘non-self’ antigen by binding to it to its receptor site
•
Requires a helper T- Cell to activate the B Cell
•
Once activated by a Helper T Cell, it divides madly producing two types of
daughter cells including:
• Plasma B cells
• Memory B Cells
These cells are clones of the original activated cell and thus produce the same
antibody. This is known as the Clonal Selection Theory (see page 255)
•
58
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
B-Cells in Action
59
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
B-memory Cells
• when the plasma cells produce new antibodies and b-cells,
some produced differentiate into other cells called b-memory
cells.
• B-Memory cells have the same antigen-antibody specificity as
the original parent b-cell.
• memory cells can survive for many years or even life.
• if a second infection ever occurs, the b-memory cells react
faster and more vigorously than the initial infection.
• remain in circulation, producing small quantities of antibody
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
B-Plasma Cells
• Produce and secrete huge quantities of antibody molecules
• These antibodies bind with antigens forming an antibodyAntigen complex
• Plasma cells are relatively short living & broken down
following infection
Chapter 8 - Defence Against Disease
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Chapter 8 - Defence Against Disease
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Topic CHP 8.11 Questions:
1. When an antigen enters the body it probably passes many B cells before it meets one with
the immunoglobulan with which it can combine. In effect the antigen ‘selects’ the B cell that
will lead to its death. This selection process is called: ________________________
2. True/ False: B cells reproduce by meiosis
3. True/ False: cloned cells have identical DNA
4. Once activated by a Helper T cell, B cells divide into 2 cells: ___________________,
___________________________
5. Memory cells can last in the body for how long (roughly): 2 weeks; 2 months, 2 years, 20
years, a life time
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
T Cells
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
T-Cells
• When T-cells mature in the thymus, many different types of T-cells
are produced which recognise many different antigens.
Helper
Cells
Types of
T -T -Cells
Cytotoxic (Killer) T Cells
Memory T Cells
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CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
T-Cells
• When T-cells mature in the thymus, many different types of T-cells are
produced which recognise many different antigens.
Types of T - Cells
Helper T - Cells
Cytotoxic (Killer) T Cells
Memory T Cells
Helper T-cells (Th)
• Release chemicals which attract phagocytes
• Stimulate cell division in B-Cells
• Produce chemicals that stimulate other T Cells
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CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
T-Cells
Cytotoxic T-Cells (Tc)
•
Another type of T-cell, cytotoxic T-cells (Tc), kills body cells that have been
infected with a virus.
•
Tc cells kill the infected cell by secreting proteins that punch holes in the
membrane of the cell and the contents ooze out.
•
Tc cells can only kill a virus when it is inside a cell.
•
Some Tc cells also destroy cancer cells.
Suppressor T Cells (Tsc)
• regulates immune response by turning it off when the infection
passes
Chapter 8 - Defence Against Disease
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CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
Cytotoxic T-Cells (Tc)
• Another type of T-cell, cytotoxic T-cells (Tc), kills body cells that have been
infected with a virus.
• Tc cells kill the infected cell by secreting proteins that punch holes in the
membrane of the cell and the contents ooze out.
• Tc cells can only kill a virus when it is inside a cell.
• Some Tc cells also destroy cancer cells.
Memory T Cells (Tm)
• Remain in circulation (spleen) for many years after infection
Chapter 8 - Defence Against Disease
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Topic CHP 8.12 Questions:
1. T cells get their name from which gland in the body? __________
2. List the three types of T Cells:
_________________________, ________________________, ____________________
3. Outline 2 functions of T Helper (Th) Cells:
4. What is the role of Suppressor T Cells:
CHP 8 TOPIC 13: PATHOGENIC RESPONSES TO IMMUNITY
Pathogenic Adaptations They Fight Back!
Some of the mechanisms which make them less likely to be attacked or killed include:
1. Antigenic variation: some populations of pathogens change their surface antigens as they
grow and reproduce in the host – the body has no immunity to the new antigens
2. Immunity to digestive enzymes: some survive inside a phagocyte, others are able to burrow
out of digestive sacs (lysosomes) in phagocytes
3. Spore production: some produce spores resistant to attack (fungi)
4. Resistant cysts: some produce and live in resistant cysts (some bacteria)
5. Living inside host cells: some avoid attack by living inside host cells
6. Attack immune system of host: may produce toxins (exotoxins) that destroy cells or enzymes
to attack leukocytes
CHP 8 TOPIC 14 HUMORAL vs CELL MEDIATED
Summary of similarities and differences between humoral and cell mediated immunity
HUMORAL IMMUNITY
CELL-MEDIATED
IMMUNITY
Cells Involved
b lymphocytes produced and
matured in the bone marrow
T- Lymphocytes, produced in bone
marrow and mature in the thymus
Targets
Invading pathogens, particularly
bacteria, viruses, and toxins
Eukaryotic cells bearing non self
antigens; cancerous cells, cells
infected with cancer, transplanted
tissue
Principal Weapons
Secrete large amounts of antibody
Secrete chemicals which destroy
eukaryotic cell membranes
Variety Of Cells
Plasma cells and memory cells
Helper T cells, cytotoxic T cells and
memory T cells
Recognition Of Antigens
Immunoglobulins on surface of B cell
T cell receptors (immunoglobulins)
on cell surface
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CHP 8 TOPIC 15 IMMUNITY
After coming into contact with a pathogen and surviving , you will be immune
to the pathogen for many years, often for life. This immunity is due to the
presence of antibody in your circulation and the presence of memory
cells. Immunity has been acquired!
• The second immune response (secondary response) is faster and bigger
than the first
• The second infection may not even produce symptoms (plasma cells
destroy pathogen before symptoms appear
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CHP 8 TOPIC 15 IMMUNITY
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CHP 8 TOPIC 15 IMMUNITY
Type of Immunity
Mechanism
Duration of Immunity
Natural
After infection with a pathogen, circulation
contains some antibodies and memory cells
Long lived immunity,
years or for life
Induced
After vaccination (with attenuated
pathogen) circulation contains some
antibodies and memory cells
Natural
Antibodies cross the placenta from mother Short lived. The baby has
to child in the developing fetus. Breast milk
no plasma cells or
alos contains some antibodies
memory cells to
continue antibody
production
Induced
At times of high risk of infection you may
receive injections of antibodies. Antitoxins
are antibodies specific to toxins. Antivenins
are antibodies specific to toxin in snake or
insect bites
Active
Immunity
Passive
Immunity
Long lived immunity,
years or for life
Short lived: no plasma
cells or memory cells to
continue antibody
production74
Topic CHP 8.15 Questions:
1. List three things pathogens can do to fight the immune response:
________________________, _______________________, ____________________
2. Outline:
–
–
: One similarity between Humoral immunity & Cell mediated immunity
One difference between Humoral immunity & Cell mediated immunity
Humoral immunity
Similarities
Differences
Cell mediated immunity
CHP 8 TOPIC 16 VACCINES
• Are used to induce active immunity
• Involves introducing a pathogens antigen into the host
• Host responds by producingantibodis and memory cells specific to
pathogen
• Vaccines are solutions, usually injected which contain:
– Bacteria which have been killed
– Live attenuated (weakened) bacteria or viruses. These usually retain the ability to live
and/ or reproduce but no longer cause disease
– Toxoids: these are chemical copies of bacterial toxins, inactivated so they cannot cause
disease
• Immunization acts like a primary infection
• Herd immunity: from large scale immunization programs
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CHP 8 TOPIC 17 ALLERGIES AND HYPERSENTSITIVITY
Allergies and Hypersensitivity
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CHP 8 TOPIC 17 ALLERGIES AND HYPERSENTSITIVITY
Allergies and Hypersensitivity
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