Download - UNIT THREE
UNIT THREE
BIOLOGYAREA 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).
Chapter 8 - Defence Against Disease 4
CHP 8 TOPIC 1: The Lymphatic System
Leukocytes, we will come back to these in more detail!
LEUKOCYTESAll produced in the Bone Marrow from Stem Cells
Granular Leukocytes
Have large, lobbed nuclei and distinctive granules in their cytoplasm
Agranular Leukocytes
Cytoplasm usually lacks granules and the nucleus is more rounded
Neutrophils
•Most numerous WBC•Main phagocytotic cell•Ingest bacteria and phagocytize dead cells• short lived
Eosinophils
•Produce enzymes which detoxify foreign proteins and fight parasatistic infection
Basophils
•Produce and release heparin (anticoagulant) and histamine in response to injury or infection
Lymphocytes
(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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CHP 8 TOPIC 1: The Lymphatic System
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: ________________________
Immune System: Consists of Three Lines of Defence
Chapter 8 - Defence Against Disease 7
Pathogen invades Tissue/ Cell
Non Specific Defence Specific Defence
Barriers
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Physiological
Mechanisms
ChemicalMechanisms
Phagocytes and
NK Cells
InflammationBasophils
Mast Cells and platelets
Histamines & phagocytosis
B Cells
T Cells
Memory Cells
Antibodies
Humoral Immunity
Cell Mediated Immunity
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CHP 8 TOPIC 2: THREE LINES OF DEFENCE
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Non-specific mechanisms: Physical and Barriers: 1st line of defence
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Physical 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
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Chemical Barriers• 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– 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
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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
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Chapter 8 - Defence Against Disease 12
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
CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
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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.
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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CHP 8 TOPIC 3: NON-SPECIFIC IMMUNITY – 1ST LINE
Topic CHP 8.3 Questions:
1. List two physical barriers to infection in:a) Plants: ______________________________, ________________________b) Animals: _____________________________, _______________________
2. List two chemical barriers to infection in:a) Plants: ______________________________, ________________________b) 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
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Non-specific mechanisms: Non-Specific Cellular Defences:
2nd line of defence
CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
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CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
PHYSIOLOGICAL
Non Specific Defence Action
Macrophages (big phagocytes) release chemicals (INTERLEUKIN-1) which reset the body’s thermostat in the hypothalamus, allowing temperature to rise
High temp. helps as it: • kills some pathogens• increases the activity of some lymphocytes and phagocytes• speeds up the death of virus infected cells
CHEMICALINTERFERONS are a group of antiviral chemicals, produced by some cells which have been infected with viruses
They can fight infection by:• interfering with virus replication• making unaffected cells more resistant to viruses• stimulating macrophages to destroy virus infected cells
COMPLEMENT PROTEINS there are 20 complement proteins present in body fluids. They may be activated to fight infection:Directly by the presence of pathogens, orWhen antigens and antibodies combine (see specific immunity
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
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 LINECELLULAR …
Eosinophils • can be phagocytotic.• secrete enzymes to kill parasitic worms among other pathogens
CHP 8 TOPIC 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
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
Basophils are a type of white blood cell (leukocyte). These cells help you fight infections by releasing histamine and other chemicals like heparin (antocoagulant)
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 8.4: NON-SPECIFIC IMMUNITY – 2nd LINE
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CHP 8 TOPIC 4: NON-SPECIFIC IMMUNITY – 2nd LINE
CELLULAR
Non Specific Defence ActionPHAGOCYTES
Macrophages/ Monocytes: • largest WBC• monocytes grow into macrophages
Phagocytes engulf, ingest, digest and destroy invading pathogens, damaged cells and debris. They can destroy up to 100 bacteria before dying themselvesNeutrophils:
• most numerous WBC• main phagocytotic cell• ingest bacteria and phagocytize dead cellsEosinophils: • can be phagocytotic.• secrete enzymes to kill parasitic worms among other pathogens
Natural Killer (NK) CellsA 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 CellsLarge 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)
BasophilsGranular leukocytes present in blood. Important in inflammatory response
Release histamine and seratonin
Platelets cell fragments circulating in blood Also release histamine and involved in clotting of blood
Topic CHP 8.4Questions: 2nd Line of DefenceFEATURE PRODUCED/
FOUNDFUNCTION 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 24
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
Pathogens Enter Tissues
Platelets
Basophils
Mast Cells
Complement Proteins
Blood vessels dilate
Produce Histamine and seratonin etc
Increased blood flow to
region
Capillaries become
permeable and leaky
Phagocytes move to an
area
Redness
Heat
Edema
Pus
Increased phagocytosis
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CHP 8 TOPIC 5: THE INFLAMMATORY RESPONSE
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The Cause of Fever
CHP 8 TOPIC 5: FEVER - PYREXIA
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.
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Specific Immunity 3nd Line of defence
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CHP 8 TOPIC 6: SPECIFIC IMMUNITY -INTRODUCTION
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STEM CELLSBone Marrow- specialise into blood cells
Lymphocytes Develop in bone marrow
NK Cells(see non-specific defences)
Thymus processing
Mature B Cells(see non-specific defences)
Mature T Cells(see non-specific defences)
Migrate to Lymph nodes Migrate to Lymph nodes
Memory T Cells Helper T Cells Cytotoxic T Cells
Memory B Cells Plamsa B Cells
CHP 8 TOPIC 6: SPECIFIC IMMUNITY -INTRODUCTION
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: _________________
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
How Does The Body Know What Cells To Attack
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
Chapter 8 - Defence Against Disease 38
Blood Groups – Blood Antigens
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
• 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 Rh- and comes into contact with RH+ blood will respond by producing antibodies against the antigen. This can become critical in pregnancy
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Rhesus Incompatibility
CHP 8 TOPIC 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
Chapter 8 - Defence Against Disease 41
Rhesus Incompatibility
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 7: SPECIFIC IMMUNITY -SELF AND NON-SELF
B & T Cells: A partnership
CHP 8 TOPIC 9 B & T CELLS – SOLDIERS IN ARMS
SPECIFIC IMMUNITY
Humoral Immunity- B Cells(Antibody Mediated)
Cell Mediated Immunity – T Cells
B Cellreceptor (immunoglobuln)
binds with antigenCLONAL SELECTION
antigen
T Helper Cellbinds with b cell
Releases chemicals to attract phagocytes
B Memory Cells
B Plasma Cells
T Cells
Cytotoxic T CellsT Memory 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
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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.
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Chapter 8 - Defence Against Disease 50
The Structure of Antibodies
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Chapter 8 - Defence Against Disease 52
Action of Antibodies
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Chapter 8 - Defence Against Disease 53
Action of Antibodies
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Antibodies in summary …
CHP 8 TOPIC 10: ANTIBODIES & IMMUNOGLOBULINS
Topic CHP 8.10 Questions:
1. True/ False: B and T cells produce immunoglubulins2. Draw an antibody in the space below labelling: heavy chain(s), light chain(s), variable region
3. True/ False: Antibodies are long lasting molecules
• 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 56
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
Clonal selection TheoryWhen 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 57
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)
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CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
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B-Cells in Action
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
Chapter 8 - Defence Against Disease 60
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
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
Chapter 8 - Defence Against Disease 61
B-Plasma Cells• Produce and secrete huge quantities of antibody molecules
• These antibodies bind with antigens forming an antibody-Antigen complex
• Plasma cells are relatively short living & broken down following infection
CHP 8 TOPIC 11: HUMORAL (Antibody mediated) IMMUNITY
Chapter 8 - Defence Against Disease 62
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
T Cells
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
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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 - CellsHelper T - Cells Cytotoxic (Killer) T Cells Memory T Cells
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
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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 (Th)
• Release chemicals which attract phagocytes• Stimulate cell division in B-Cells• Produce chemicals that stimulate other T Cells
Helper T - Cells Cytotoxic (Killer) T Cells Memory T Cells
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
Chapter 8 - Defence Against Disease 67
T-CellsCytotoxic 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
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
Chapter 8 - Defence Against Disease 68
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
CHP 8 TOPIC 12 CELL MEDIATED IMMUNITY – T CELLS
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:
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 13: PATHOGENIC RESPONSES TO IMMUNITY
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CHP 8 TOPIC 14 HUMORAL vs CELL MEDIATED
Summary of similarities and differences between humoral and cell mediated immunity
HUMORAL IMMUNITY CELL-MEDIATEDIMMUNITY
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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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
CHP 8 TOPIC 15 IMMUNITY
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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
Active 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
Long lived immunity, years or for life
Passive Immunity
Natural Antibodies cross the placenta from mother to child in the developing fetus. Breast milk alos contains some antibodies
Short lived. The baby has no plasma cells or
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
Short lived: no plasma cells or memory cells to
continue antibody production
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 Cell mediated immunity
Similarities
Differences
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• 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
CHP 8 TOPIC 16 VACCINES
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Allergies and Hypersensitivity
CHP 8 TOPIC 17 ALLERGIES AND HYPERSENTSITIVITY
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Allergies and Hypersensitivity
CHP 8 TOPIC 17 ALLERGIES AND HYPERSENTSITIVITY