Cell recognition and the immune system

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What are two defence mechanisms called that use lymphocytes?
1. T lymphocytes cell mediated response 2. B lymphocytes humoral response
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Lymphocytes must be able to recognise what are non-sef cells within the body. How do they do this?
Each cell has special molecules on its surface. Within these molecules it is the protein that is important as they have a highly specific tertiary structure and it is this tertiary structure that allows cells to be distinguished from one another.
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It is the proteins of a molecule which allow the immune system to identify what 4 things?
1. Pathogens 2. non self material 3. toxins 4. abnormal body cells
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How do lymphocytes recognise cells belonging to the body? (part 1)
In the fetus lymphocytes are constantly colliding with other cells. Infection is rare in the fetus because it is protected by the mother and the placenta. This means these lymphocytes collide with the body's own material.
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How do lymphocytes recognise cells belonging to the body? (part 2)
Some lymphocytes have receptors that fit the body's own cells. These will either die or be suppressed so the only remaining lymphocytes are those that don't fit the body's own cells
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If the first physical and chemical (skin and saliva) barrier fail the next line of defence are the white blood cells. What are the 2 types of white blood cells?
Phagocytes and Lymphocytes
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What do phagocytes do to pathogens?
They carry out phagocytosis which is where they ingest and destroy them.
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What is the 5 step process to phagocytosis? (part 1)
1. The phagocyte is attracted to the pathogen by the chemical products of the pathogen. Moving toward the pathogen across a concentration gradient. 2. The phagocytes receptors attach to chemicals on the surface of the pathogen.
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What is the 5 step process to phagocytosis? (part 2)
3. Lysosomes within the phagocyte migrate towards the phagosome formed by engulfing the bacterium. 4. The lysosomes release their lysozymes into the phagosome where they hydrolyse the bacterium 5. The hydrolysis products of the bacterium are absorbed
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What is an antigen?
A protein that is recognised as non self material to your body and stimulates an immune response
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What is the difference between phagocytes and lymphcytes?
Phagocytes are nonspecific whereas lymphocytes are specific. Lymphocytes are slow and phagocytes are fast. Phagocytes are short term by lymphocytes are lon time
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What are the two types of lymphocytes?
B and T lymphocytes
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What are B lymphocytes?And where do they mature?
They mature in the bone marrow and are associated with humoral immunity.
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What is humoural immunity?
Immunity involving antibodies that are present in body fluid or 'humour' such as blood plasma
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What are T lymphocytes? And where do they mature?
They mature in the thymus gland and are associated with cell mediated immunity.
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What is cell mediated immunity?
Immunity involving body cells
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T lymphocytes can distinguish invader from normal cells because:
1. Phagocytes have engulfed & hydrolysed a pathogen 2. Body cells invaded by a virus present viral antigens on their surface 3. Transplanted cells from individuals have different antigens 4. Cancer cells also present different antigens
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What are cells that present foreign antigens on their surface called?
Antigen-presenting cells
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What is the process of cell mediated immunity? (part 1)
1. Pathogen invade body cell or is taken in by phagocyte 2. The phagocyte places antigens from the pathogen on its cell surface membrane 3. Receptors on a specific T helper cell fit exactly onto these antigens
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What is the process of cell mediated immunity? (part 2)
4. This attachment activates the T cell to undergo mitosis and form a clone of identical cells
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What do the cloned cells do in cell mediated immunity?
A. develop into memory cells B. Stimulate phagocytes to engulf pathogens by phagocytosis C. Stimulate B cells to divide and secrete their antibody D. Activate cytotoxic T cells
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How do cytotoxic T cells kill infected cells?
They produce a protein called perforin that makes holes in cell surface membrane. The holes now mean the cell membranes becomes freely permeable to all substances and the cell des because of this
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When an antigen enters the blood, there will be one B cell that has an antibody on its surface that is complimentary to the antigen. The antibody then attaches itself to the antigen. The antigen enters the B cell by what method?
Endocytosis
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What happens after endocytosis in humoral immunity?
The T helper cells bind to the processed antigens that are now present on the B cells surface, and stimulate the B cell to divide by mitosis to form clones all of which produce the antibody to fit the antigen. This is called clonal selection
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What are monoclonal antibodies?
Each clone of a B cell produces its own type of antibody which are referred to as monoclonal antibodies
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In each clone of a B cell there are two types of cells produced:
Plasma cells and memory cells
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What are plasma cells?
The secrete antibodies into the blood plasma it is known as the primary immune response
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What are memory cells?
They are responsible for the secondary immune response and when they come into contact with the antigen again they will divide into plasma cells in order to kill the antigen so have long term immunity
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What is the 6 process of humoral immunity? (part 1)
1. The surface antigens of an invading pathogen are taken up by a B cell 2. The B cell processes the antigens and presents them on its surface 3. Helper T cells attach to the processed antigens on the B cell and so activating the B cell.
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What is the 6 process of humoral immunity? (part 2)
4. Now it is activated it divides by mitosis to a give clone of plasma cells 5. The cloned plasma cells produce and secrete antibodies which attaches to the antigen and kills the pathogen 6. Some develop into memory cells
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What are antibodies?
Proteins with specific binding sites synthesised by B cells
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What are antibodies made up of?
4 polypeptide chains
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What is the structure of an antibody?
*
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How does an antibody cause the destruction of an antigen?
They cause agglutination of the bacterial cells. And clumps of the cells are formed making it easier for the phagocytes to locate them and are less likely to spread through the body. Then then serve as markers for the phagocytes to find and kill
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What are the 3 main uses of monoclonal antibodies?
1. Targeting medication to specific cell types by attaching a therapeutic drug to an antibody 2. Medical diagnosis 3. Pregnancy testing
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What is an example of targeting medication to specific cell types by attaching a therapeutic drug to an antibody?
Monoclonal antibodies are produced that are specific to antigens on cancer cells. The antibodies are given to a patient & attach themselves to the receptors on their cancer cells & then block the chemical signals that stimulate uncontrolled growth
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What is an example of monoclonal antibodies being used in medical diagnosis?
They are used for diagnosis for things such as influenza.
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How are monoclonal antibodies used in pregnancy testing?
The placenta produces the hormone (hCG) which is found in the mothers urine. Monoclonal antibodies are present on the ***** of the pregnancy test and are linked to coloured particles. If hCG touches the ***** it binds to these antibodies.
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What are the ethics behind monoclonal antibodies?
1. They ar tested on rats 2. Been successful at treating diseases 3. Testing on other people
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What is passive immunity?
Introducing antibodies to the individual from an outside source. No memory cells are produced because the antibodies never come in contact with a pathogen or its antigens. This also means the antibodies will be used up & they cannot be produced again
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What is active immunity?
Produced by stimulating the production of antibodies by the individuals' own immune system. Direct contact with the pathogen is needed.
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There are two types of immunity what are they and explain them:
Natural active immunity - individual is infected under normal circumstances and body produces its own antibodies Artificial active immunity - from vaccination
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What are the features of a successful vaccination programme?
1. Economically available 2. Few side effects 3. There are means of producing, storing and transporting the vaccine 4. Administration must be proper 5. Herd immunity
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What is herd immunity?
A large proportion of the population has been vaccinated.
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Why may vaccination not eliminate disease?
1. Fails to induce immunity in certain people 2. People may develop the disease immediately after vaccination 3. There are some many varieties of pathogens that its impossible to create a vaccine for them all. 4. Some pathogens hide inside body cells
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What is the structure of the HIV virus?
*
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How can HIV replicate if it cannot replicate itself?
It uses genetic material to instruct host cells' biochemical mechanisms to produce the components required to make new HIV.
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How does HIV use host cells to replicate? (part 1)
1. Following infection HIV enters the bloodstream and circulates around the body 2. A protein on the HIV binds readily binds to a protein called CD 4. HIV most frequently attached to helper T cells
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How does HIV use host cells to replicate? (part 2)
3. The protein capsid fuses with the cell surface membrane. The RNA & enzymes of HIV enter the helper T cell. 4. The HIV reverse transcriptase converts the viruses RNA into DNA
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How does HIV use host cells to replicate? (part 3)
5. The newly made DNA is moved into helper T cells nucleus where it is inserted into the cells DNA 6. The HIV DNA in the nucleus creates messenger RNA using the cell's enzymes. This mRNA contains instructions for making new viral proteins and the RNA
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How does HIV use host cells to replicate? (part 4)
7. The mRNA passes out of the nucleus through a nuclear pore and uses the cells the cell's protein synthesis mechanisms to make HIV particles 8. The HIV particles break away from the helper T cell with a piece of its cell surface membrane which forms
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How does HIV use host cells to replicate? (part 4b )
their lipid envelope
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How does HIV cause the symptoms of AIDS?
HIV causes a decrease in helper t cells which ultimately causes a decrease in B cell and memory cells so the immune system cannot function properly causing the person to suffer badly from a common cold.
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What is the ELISA test?
Enzyme linked immunosorbent assay. It uses antibodies to detect the amount of protein in a sample
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What is the procedure of the ELISA test? (part 1)
1. Apply the sample to a surface 2. Wash the surface several times to remove any unattached antigens. 3. Add the antibody that is specific to the antigen we are trying to detect and leave the 2 to bind together.
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What is the procedure of the ELISA test? (part 2)
4. Wash the surface to remove any excess antibodies. 5. Add a second antibody that binds with the first antibody. This second antibody has an enzyme attached to it. 6. Add the colourless substrate of enzyme.
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What is the procedure of the ELISA test? (part 3)
The enzyme acts on the substrate to change it into a coloured product 7. The amount of the antigen present is relative to the intensity of colour that develop
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Why are antibiotics ineffective to viruses such as AIDS?
HIV has a protein coat and not a murein cell wall which antibiotics are used to break. Also viruses hide inside host cells where antibiotics cannot reach them.
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Card 2

Front

Lymphocytes must be able to recognise what are non-sef cells within the body. How do they do this?

Back

Each cell has special molecules on its surface. Within these molecules it is the protein that is important as they have a highly specific tertiary structure and it is this tertiary structure that allows cells to be distinguished from one another.

Card 3

Front

It is the proteins of a molecule which allow the immune system to identify what 4 things?

Back

Preview of the front of card 3

Card 4

Front

How do lymphocytes recognise cells belonging to the body? (part 1)

Back

Preview of the front of card 4

Card 5

Front

How do lymphocytes recognise cells belonging to the body? (part 2)

Back

Preview of the front of card 5
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