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


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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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


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


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


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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



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


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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.


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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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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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


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


Platelets

• cell fragments circulating in blood

• also release histamine and involved in clotting of blood


http://biomed.brown.edu/Courses/BI108/BI108_2005_Groups/10/webpages/creditslink.htm#creditspic

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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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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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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


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


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’



Blood Groups – Blood Antigens


• 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



Rhesus Incompatibility


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.


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


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.


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


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


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


The Structure of Antibodies



Action of Antibodies



Action of Antibodies


Antibodies in summary …



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



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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B-Cells in Action



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



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




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


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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



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



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



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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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


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

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UNIT THREE