DEFENCE AGAINST INFECTIOUS DISEASE - St Leonard's College
DEFENCE AGAINST INFECTIOUS DISEASE AHL Topic 11.1 IB Biology Miss Werba AHL TOPIC 11 FURTHER PHYSIOLOGY J WERBA IB BIOLOGY 2 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 J WERBA IB BIOLOGY 3 11.1.1 BLOOD CLOTTING Command term = DESCRIBE Blood clotting is involves a chain of biochemical reactions. It forms part of the bodys first line of defence against disease. Allows us to seal wounds and prevent excess
blood loss. J WERBA IB BIOLOGY 4 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 J WERBA IB BIOLOGY 5 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. J WERBA IB BIOLOGY 6 11.1.1 BLOOD CLOTTING Command term = DESCRIBE 1. Wound exposes collagen layer in extracellular matrix. 2. Platelets adhere to exposed collagen and degranulate, releasing contents of their granules.
3. This promotes further platelet adhesion and formation of a platelet plug. 4. The damaged tissue initiates coagulation by releasing clotting factors and triggering a cascade of reactions that activate Factor X. J WERBA IB BIOLOGY 7 11.1.1
BLOOD CLOTTING Command term = DESCRIBE 5. Activated Factor X binds and activates Factor V, forming prothombinase. 6. Prothombinase coverts prothrombin (Factor II) to thrombin. 7. Thrombin converts fibrinogen (Factor I) to fibrin. 8. Fibrin is a fibrous protein
and forms an insoluble mesh. 9. Red blood cells (RBCs) and platelets get trapped in the mesh the clot. J WERBA IB BIOLOGY 8 11.1.1 BLOOD CLOTTING Command term = DESCRIBE Platelets Prothrombin in
plasma Damaged blood vessels. Exposure to air. Clotting factors Thrombin Fibrinogen (soluble) Fibrin fibres (insoluble) RBCs J WERBA IB BIOLOGY
CLOT 9 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE J WERBA IB BIOLOGY 10 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 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 J WERBA IB BIOLOGY 12 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE ANTIGEN PRESENTATION: 1. 2. 3.
4. 5. Pathogen invades the body. The pathogens antigen is detected as non-self by macrophages. Macrophage try to ingest the pathogen (phagocytosis) but the ingestion isnt complete. Macrophage displays the bacterial antigen on its own cell membrane. Macrophage has become an antigen presenting cell (APC). J WERBA IB BIOLOGY 13
11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE ANTIGEN PRESENTATION: Antigen is absorbed and then displayed by the macrophage MHC protein J WERBA IB BIOLOGY Antigen presentation by macrophage 14
11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE HELPER T CELL ACTIVATION: 1. 2. 3. 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. J WERBA IB BIOLOGY 15 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE HELPER T CELL ACTIVATION: Macrophage sends a signal to activate the helper T-cell Inactive Helper T-cell Active Helper T-cell
J WERBA IB BIOLOGY 16 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE B CELL ACTIVATION: 1. 2. The TH cells activate complementary B cells The B cells also divide to form a clone.
J WERBA IB BIOLOGY 17 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE B CELL ACTIVATION: Active Helper T-cell Antibody Active B-cell Inactive B-cell
J WERBA IB BIOLOGY Activated Helper T-cell Activated sends aHelper signal T-cell to binds tothe B-cell activate B-cell 18 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE PLASMA CELL FORMATION:
1. 2. 3. Activated B cells differentiate into plasma cells. Plasma cells make large amounts of antibody proteins. The antibodies are secreted by exocytosis. J WERBA IB BIOLOGY 19 11.1.2 THE IMMUNE RESPONSE Command term = OUTLINE
MEMORY CELL FORMATION: 1. 2. 3. 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) J WERBA IB BIOLOGY
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 J WERBA IB BIOLOGY 23 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. J WERBA IB BIOLOGY 24 11.1.4 ANTIBODY PRODUCTION Command term = EXPLAIN
What happens after the antibody has bound to the antigen? Enhances phagocytosis http://kvhs.nbed.nb.ca/ J WERBA IB BIOLOGY gallant/biology/ Leads to cell lysis 25 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 J WERBA IB BIOLOGY 26 11.1.3
IMMUNITY Command term = DEFINE J WERBA IB BIOLOGY 27 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 J WERBA IB BIOLOGY 28 11.1.6 VACCINATIONS Command term = EXPLAIN J WERBA IB BIOLOGY 29 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 J WERBA IB BIOLOGY 30 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 - havent really studied what happens when a mixture of antigens are presented together (eg. MMR vaccination) Artificial immunity is less effective J WERBA IB BIOLOGY 31 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. J WERBA IB BIOLOGY 32 11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE PRODUCTION: 1. A mammal (eg. mouse) is injected with the antigen. 2. The mouse plasma cells will produce antibodies against the antigen. 3. The mouse plasma cells complementary to the antigen are extracted and fused with tumour cells form a hybridoma cell 4. The hybridoma cell divides and produces identical antibodies to the original plasma cells 5. The antibody can then be harvested. J WERBA IB BIOLOGY 33 11.1.5
MONOCLONAL ANTIBODIES Command term = DESCRIBE J WERBA IB BIOLOGY 34 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 J WERBA IB BIOLOGY 35 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
J WERBA IB BIOLOGY 36 Sample questions Q2. State one use of monoclonal antibodies in diagnosis and one use in treatment.  Q3. Outline the principle of immunity. J WERBA IB BIOLOGY  37 Sample questions
A1. B A2. Diagnosis: 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; J WERBA IB BIOLOGY 2 max 38
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; J WERBA IB BIOLOGY 39
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