1. DEFENCE AGAINST INFECTIOUS DISEASE
AHL Topic 11.1
IB Biology
Miss Werba

2. AHL TOPIC 11 – FURTHER PHYSIOLOGY
11.1 DEFENCE AGAINST INFECTIOUS DISEASE
11.2
MUSCLES & MOVEMENT
11.3
THE KIDNEY
11.4
REPRODUCTION
J WERBA – IB BIOLOGY 2

3. THINGS TO COVER Blood clotting & thrombin
Challenge & response principle
Clonal selection for immunity
Memory cells for immunity
Passive & active immunity
Antibody production
Monoclonal antibodies for diagnosis & treatment
Vaccinations
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4. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
Blood clotting is involves a chain of biochemical reactions.
It forms part of the body’s first line of defence against disease.
Allows us to seal wounds and prevent excess blood loss.
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5. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
Blood clotting involves platelets.
Platelets are fragments of much larger cells.
They contain granules filled with chemicals that act in the clotting process, including:
Serotonin
Ca2+ ions
Enzymes
ADP
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6. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
A blood clot consists of:
a plug of platelets within a
network of insoluble fibrin fibres
Aggregation of platelets and fibrin formation both require the proteolytic enzyme thrombin.
Clotting also requires:
calcium ions
a dozen or so protein clotting factors.
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7. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
Wound exposes collagen layer in extracellular matrix.
Platelets adhere to exposed collagen and degranulate, releasing contents of their granules.
This promotes further platelet adhesion and formation of a platelet plug.
The damaged tissue initiates coagulation by releasing clotting factors and triggering a cascade of reactions that activate Factor X.
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8. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
Activated Factor X binds and activates Factor V, forming prothombinase.
Prothombinase coverts prothrombin (Factor II) to thrombin.
Thrombin converts fibrinogen (Factor I) to fibrin.
Fibrin is a fibrous protein and forms an insoluble mesh.
Red blood cells (RBCs) and platelets get trapped in the mesh – the clot.
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9. BLOOD CLOTTING Command term = DESCRIBE
11.1.1
BLOOD CLOTTING Command term = DESCRIBE
Platelets
Damaged blood vessels. Exposure to air.
Prothrombin in plasma
Clotting factors
Thrombin
Fibrinogen (soluble)
Fibrin fibres
(insoluble)
RBCs
CLOT
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10. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
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11. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
1st line of defence:
unbroken skin, mucous secretions, body secretions, gut
2nd line of defence:
Inflammation  increases blood flow
Non-specific cellular response  platelets, leucocytes
Fever  kills pathogens; increases activity of IS
Protein responses  complement, interferon
J WERBA – IB BIOLOGY 11

12. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
3rd line of defence:
Involves the immune response
Antigen presentation
Activation of Helper T cells
Activation of B cells
Production of plasma cells
Production of memory cells
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13. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
ANTIGEN PRESENTATION:
Pathogen invades the body.
The pathogen’s antigen is detected as “non-self” by macrophages.
Macrophage try to ingest the pathogen (phagocytosis) but the ingestion isn’t complete.
Macrophage displays the bacterial antigen on its own cell membrane.
Macrophage has become an antigen presenting cell (APC).
Pathogen invades
Phagocytosis
Antigen presenting cell (APC) formation
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14. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
ANTIGEN PRESENTATION:
Antigen is absorbed and then displayed by the macrophage
Antigen presentation by macrophage
MHC protein
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15. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
APC presents antigen to lymphocytes
Activates complementary Helper T cell
Helper T cell divides
HELPER T CELL ACTIVATION:
The APC comes into contact with lymphocytes.
A Helper T (TH) cell complementary to the antigen on the APC will be identified.
Selected TH cell divides by mitosis forming a clone.
These processes are known as clonal selection & clonal expansion.
Memory T cells are also formed.
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16. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
HELPER T CELL ACTIVATION:
Inactive Helper T-cell
Macrophage sends a signal to activate the helper T-cell
Active Helper T-cell
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17. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
B CELL ACTIVATION:
The TH cells activate complementary B cells
The B cells also divide to form a clone.
Helper T cell presents antigen to B cells
Activates complementary B cell
B cell divides
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18. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
B CELL ACTIVATION:
Active Helper T-cell
Antibody
Activated Helper T-cell sends a signal to activate the B-cell
Activated Helper T-cell binds to B-cell
Inactive B-cell
Active B-cell
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19. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
PLASMA CELL FORMATION:
Activated B cells differentiate into plasma cells.
Plasma cells make large amounts of antibody proteins.
The antibodies are secreted by exocytosis.
Differentiation of B cell
Plasma cell formation
Antibody production
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20. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
MEMORY CELL FORMATION:
Activated B cells also differentiate into memory B cells.
Memory cells remain after immune response.
Allow a rapid response if the disease is encountered again (= LONG TERM IMMUNITY)
Differentiation of B cell
Plasma cell formation
Antibody production
Memory B cell formation
Long term immunity
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21. 11.1.2
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22. THE IMMUNE RESPONSE Command term = OUTLINE
11.1.2
THE IMMUNE RESPONSE Command term = OUTLINE
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23. ANTIBODY PRODUCTION Command term = EXPLAIN
11.1.4
ANTIBODY PRODUCTION Command term = EXPLAIN
Antibodies (immunoglobulins): proteins produced as a response to the presence of an antigen.
General structure of an antibody:
2 antigen-binding sites
MHC proteins (major histocompatibility complex)
T cell receptors do not respond to antigens unless the antigens are associated with MHC proteins
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24. ANTIBODY PRODUCTION Command term = EXPLAIN
11.1.4
ANTIBODY PRODUCTION Command term = EXPLAIN
The antibodies produced by a plasma cell are complementary to the original antigen presented on the pathogen.
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25. ANTIBODY PRODUCTION Command term = EXPLAIN
11.1.4
ANTIBODY PRODUCTION Command term = EXPLAIN
What happens after the antibody has bound to the antigen?
Enhances phagocytosis
Leads to cell lysis
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26. IMMUNITY Command term = DEFINE
11.1.3
IMMUNITY Command term = DEFINE
Immunity: having sufficient biological defences against infection
Active immunity: immunity due to the production of antibodies by the organism itself after the immune response has been stimulated by a pathogen
Passive immunity: immunity due to acquisition of antibodies from another organism in which active immunity has been stimulated
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27. IMMUNITY Command term = DEFINE
11.1.3
IMMUNITY Command term = DEFINE
Acquired immunity
Naturally acquired
Active
Infection; contact with pathogen
eg. chicken pox immunity
Passive
Antibodies pass from mother to baby
eg. via placenta & colostrum
Artificially acquired
Vaccine; dead or attenuated pathogens eg. MMR vaccine
Injection of antiserum eg. rabies treatment
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28. VACCINATIONS Command term = EXPLAIN
11.1.6
VACCINATIONS Command term = EXPLAIN
The secondary response to an antigen is much faster and stronger than the first response.
Vaccinations deliberately expose someone to a disease so that they develop immunity – without them having to contract the illness itself.
Vaccines contain a form of the pathogen or toxin that has been modified (attenuated) so that it is unable to harm the body
Exposure to an attenuated pathogen still allows the production of memory cells against the antigen
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29. VACCINATIONS Command term = EXPLAIN
11.1.6
VACCINATIONS Command term = EXPLAIN
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30. VACCINATIONS Command term = DISCUSS
11.1.7
VACCINATIONS Command term = DISCUSS
BENEFITS:
Protects the individual
Eradication of some diseases – eg. smallpox
Fewer people get certain diseases – eg. measles
Prevents disability – eg. paralysis from polio
Herd immunity – reduces spread, even to people not vaccinated, because they will probably not come into contact with the disease as frequently
Reduced economic burden on healthcare system
Prevention of pandemics and epidemics
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31. VACCINATIONS Command term = DISCUSS
11.1.7
VACCINATIONS Command term = DISCUSS
DANGERS:
Overloading the immune system - will reduce the ability to handle other infections
Could contain other harmful substances – eg. mercury now not used in vaccines
Allergies and side effects
Mixing vaccines - haven’t really studied what happens when a mixture of antigens are presented together (eg. MMR vaccination)
Artificial immunity is less effective
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32. MONOCLONAL ANTIBODIES Command term = DESCRIBE
11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE
Antibodies can be produced in a lab for therapeutic or diagnostic use.
Monoclonal antibodies are derived from a single cell.
They are pure antibody preparations that are specific for a single antigen.
The current technology for making monoclonal antibodies involves fusion of tumour cells and B cells.
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33. MONOCLONAL ANTIBODIES Command term = DESCRIBE
11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE
PRODUCTION:
A mammal (eg. mouse) is injected with the antigen.
The mouse plasma cells will produce antibodies against the antigen.
The mouse plasma cells complementary to the antigen are extracted and fused with tumour cells  form a hybridoma cell
The hybridoma cell divides and produces identical antibodies to the original plasma cells
The antibody can then be harvested.
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34. MONOCLONAL ANTIBODIES Command term = DESCRIBE
11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE
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35. MONOCLONAL ANTIBODIES Command term = DESCRIBE
11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE
USES:
Pregnancy testing
detects the presence of the HCG hormone in the urine
HCG is only released during pregnancy
Testing for a suspected heart attack
Damaged heart muscle cells release a specific cardiac enzyme into the blood
ELISA test for HIV
Colour change in dimple tray when antibodies are detected
Treatment for rabies
Diagnosis of malaria
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36. Sample questions
Q1. What are fused in the production of monoclonal antibodies?
A. Tumour cells and T cells
B. Tumour cells and B cells
C. B cells and T cells
D. Antibodies and antigens
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37. Sample questions
Q2. State one use of monoclonal antibodies in diagnosis and one use in treatment. [2] Q3. Outline the principle of immunity. [6]
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38. Sample questions A1. B A2. Diagnosis: Treatment:
detection of (antibodies to) HIV; detection of HCG / pregnancy test kits; detection of cardiac enzyme in suspected heart attacks; detection of tissue / blood type; testing for (different strains of) malaria; ELISA test;
Treatment:
targeting cancer cells with attached drugs; treatment of rabies / Ebola / lymphoma destroying T-cells to reduce rejection of transplants; 2 max
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39. Sample questions
A3.
immunity is the ability of an organism to resist infection;
due to presence of (specific) antibodies;
immunity can be active or passive;
passive due to receiving antibodies from external sources/ across placenta/from breast milk/injection;
active results from facing an infection directly/through vaccination;
pathogen/foreign cell invades body;
leads to clonal selection / formation of B memory cells;
B-cells produce specific antibodies;
if same pathogen enters body again memory cells activated / stimulated to divide;
antibodies produced faster and in greater amounts;
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