immunity for a level biology

Immunity

Lesson Objectives.

1. Understand how pathogens cause disease.2. Recall phagocytosis and the role of lysosomes

in phagocytosis.3. Know what an antigen is.4. Know that there are two types of

lymphocytes.5. Know the role of T cells in cell mediated

immunity.6. Know the role of B cells in humoral immunity.

1_3_necrosis.mov

Lymphocytes have various immune responses

• Each lymphocyte attacks a specific antigen.

1. Killer T-lymphocytes (cytotoxic T-lymphocytes) bind to cells eg those infected by viruses and kill them by lysis.

2. Helper T-Lymphocytes stimulate B-lymphocytes to divide into antibody producing plasma cells – B-lymphocytes cant work without them.

3. Plasma B-lymphocytes secrete antibodies into the blood plasma.

4. Memory B and T-lymphocytes remain in the blood for many years and produce a more effective secondary immune response to an infection which is the basis of long term immunity.

Immune response

• Invading pathogens stimulate an immune response phagocytes are the first line of response but the long term response is governed by antibodies.

• An immune response is a response to the presence of an antigen its purpose is to remove the antigen.

• Cells and molecules that are part of the body are described as self since the immune system has become desensitised to them.

• Antigens are therefore described as non self particles.

1_3_necrosis.mov

This picture shows HIV budding and bursting out of an infected cell.

Viruses are not considered to be living organisms by many biologists because they are unable to reproduce on their own.

To reproduce they must invade a host cell and use the hosts cellular mechanisms to produce new virus copies.

This budding HIV has been made by the infected cell.

hiv_life_cycle-lg.wmv

Eosinophil - In the cell's cytoplasm (yellow) are many lysomomes (purple), used to destroy invading organisms. They are capable of ingesting and destroying foreign particles by a process known as phagocytosis.

Phagocytosis – the formation of a phagosome

1_7_phagocytosis.mov

1_11_macrophage.mov

Illustration of the fluid-mosaic model of the plasma membrane.

MHCselfprotein

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Phagocytes Are Antigen-Presenting Cells

1 Phagocytosis ofthe microbialinvader

Macrophage Lymphocyte(helper T cell)


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Antigens from thedismantled invaderare attached to MHC self proteins

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MHC self protein Lymphocyte(helper T cell)


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MHC proteins andtheir attached antigens are displayed onmacrophagesurface

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Helper T cells recognize antigens and MHC proteins and bind to the macrophage, initiating a series of immune events

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Macrophages Are Antigen-Presenting Cells

1 Phagocytosis ofthe microbialinvader


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Antigens from thedismantled invaderare attached to MHC self proteins

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Helper T cells recognize antigens and MHC proteins and bind to the macrophage, initiating a series of immune events

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Cytotoxic T Cell.swf

1_12_ctl.mov

Cell Mediated immunity.

• T-lymphocytes are involved in the cell mediated response.

• They have receptors on their surfaces which bind to antigens directly. Killer T-cells then destroy the foreign cell.

• The HIV virus destroys killer T-cells.• T-lymphocytes are associated with

immune responses in tissues rather than in the blood.

t_cell_function.mov

T cells Dependent Antigens.swf

Cell mediated Immunity - The T cell immune defense

Virus

Cell Mediated immunity - The T cell immune defense

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Cell Mediated Immunity - The T cell immune defense

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Humoural Immunity - The B cell immune defense (producing antibodies)

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T cells Dependent Antigens.swf

Bacteria Viruses

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Cellular response Humoral response

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Antibodies

clonal_selection.mov

Immunoglobulin G antibody molecules, coloured transmission electron micrograph (TEM). IgG is the most abundant human immunoglobulin, and is found in all body fluids. Each Y-shaped molecule bears two arms that can bind to specific antigens, for instance bacterial or viral proteins. In doing this they mark the antigen for destruction by phagocytes, white blood cells that ingest and destroy foreign bodies. They can also kill some pathogens directly, and can neutralise toxins.

..\cells alive\ECB\media\molecular_models\04.8-antibodies.mov

antibody antigen interractions.swf

Antibody Mediated immunity.

• Antibodies make antigens harmless in one of several ways.

1. Agglutination antibodies stick to the surface of the pathogen making them clump together rendering the pathogen harmless.

2. Antibodies sticking to the surface of the pathogen causes lysis (breaking up of the foreign cell)

3. Phagocytosis – by phagocytes is speeded up.4. Precipitation – soluble toxins which are

dissolved in body fluids become solid so can no longer do harm.

5. Bacteria are prevented from attaching to the hosts cell membranes.

Humoural Immune response• When the B cells recognise a pathogen it begins

dividing rapidly into plasma cells and memory cells.

• When the pathogen has been destroyed the memory cells stay in the circulation to counteract infection if the pathogen returns.

• This gives your body an immunological memory so that your body can respond much faster when the pathogen returns – probably before symptoms appear.

• You will be naturally immune – this type of immunity where you make your own antibodies is called active immunity.

Secondary immune response.

• Not all lymphocytes become plasma cells some become memory cells which stay dormant in the blood.

• The plasma cells die once the infection is over but the memory cells don’t.

• If a second infection occurs memory cells respond immediately by producing antibodies and dividing producing more plasma cells.

• This is the secondary immune response. They secrete more antibodies more quickly this is why the secondary immune response is greater and faster.

Secondary immune response

Primary immune response caused by

the secretion of antibodies from

plasma B-lymphocytes

Secondary immune response caused by

the secretion of antibodies from

memory B-lymphocytes

Resulting in a greater faster immune

response before illness occurs.

Types of immunity and vaccinationsLesson Objectives

1. Understand the difference between passive, active immunity and herd immunity.

2. What is a vaccine?3. Understand what constitutes an effective

vaccination program.4. Why does vaccination rarely eliminate a

disease?

•Passive immunity is a temporary type of immunity.•Babies are naturally passively immune to a number of diseases when they are born because their mothers antibodies cross the placenta into their blood stream.•Babies also gain these antibodies whilst being breast fed.•They have no memory cells being formed though and after a while antibodies break down so the immunity goes.•This passive immunity allows the baby a chance for it to develop its own active immunity.

Passive immunity• Passive immunity is a temporary type of

immunity.• Babies are naturally passively immune to a

number of diseases when they are born because their mothers antibodies cross the placenta into their blood stream.

• Babies also gain these antibodies whilst being breast fed.

• They have no memory cells being formed though and after a while antibodies break down so the immunity goes.

• This passive immunity allows the baby a chance for it to develop its own active immunity.

Vaccines • Whilst your immune system is

manufacturing B-lymphocytes you suffer from a disease.

• Vaccination allows us to avoid this by building up B-lymphocytes and the antibodies needed to fight a disease without the microbe being present and increasing in numbers at the same time (which is what causes the disease)

• This means that we can get the immunity without getting the symptoms.

• Vaccine.swf• vaccination.mov

Vaccines come in various types

1. Dead pathogens eg whooping cough – the pathogen is killed but the antigens remain on the surface so the body goes through the immune response without the microorganism causing disease.

2. Non-virulent strains of pathogen (attenuated vaccine) eg rubella some strains of the disease stimulate antibody production without causing the disease.

3. Modified toxins eg Diptheria. Toxins produced by the pathogens act as antigens. The toxin can be heat treated so that it does not produce the symptoms but still triggers an immune response.

4. Isolated antigens – eg influenza sometimes the antigen can be separated from the pathogen and injected to induce an immune response.

5. Genetically engineered antigens eg Hepatitis B antigens are manufactured by genetic engineering so they can be injected without the disease developing

Artificial immunity

• Vaccines give you artificial immunity. Its active immunity because your body makes its own antibodies and will produce memory cells. To prevent the disease in the future.

• Its called artificial immunity because you have not actually caught the disease in the natural way – your body has been tricked into reacting to a harmless pathogen.

Instant immunity

• After cuts or bites people may be injected with tetanus antibodies rather that the tetanus pathogen.

• This gives you artificial immunity instantly.

• It is however passive because your B-lymphocytes have not been involved in the production of the antibodies therefore there will be no memory bells.

• The immunity will wear off when the antibodies break down.

Herd immunity

• Vaccines not only protect the people vaccinated but they reduce the occurrence of the disease – those not vaccinated are less likely to catch it.

• This is called the herd immunity effect.

• This is one of the factors which helped in the irradiation of the small pox virus following a WHO vaccination program.

• herd immunity animation.swf

Monoclonal AntibodiesLesson Objectives

1. Understand how monoclonal antibodies in enabling the targeting of specific substances and cells.

2. Evaluate methodology, evidence and data relating to the use of vaccines and monoclonal antibodies

3. Discuss ethical issues associated with the use of vaccines and monoclonal Antibodies

4. Explain the role of the scientific community in validating new knowledge about vaccines and monoclonal antibodies, thus ensuring integrity

5. Discuss the ways in which society uses scientific knowledge relating to vaccines and monoclonal antibodies to inform decision-making.

Monoclonal Antibodies.swf

http://www.sumanasinc.com/webcontent/animations/content/ELISA.html

"hybridoma" cells being multiplied in a fermenter.

http://www.sumanasinc.com/webcontent/animations/content/ELISA.html

immunity for a level biology

Documents

infected cell

foreign cell

host cell

cell mediated response

helper tlymphocytes

role of t cells

killer tcells

t cells dependent