IMMUNITY

Question	Answer
Name some parts of the body in which lymphocytes (white blood cells are found)	Blood, lymph and tissue fluid
What is the difference between specific and non specific defence mechanisms?	Non specific - don't distinguish between pathogens; respond to them all in the same way; response is immediate. Specific - distinguishes between different pathogens; takes longer but provides long lasting immunity
Give the two types of non specific mechanism	Physical barrier to entry, phagocytosis
What are the physical barriers?	Skin, mucus linings, HCl in stomach
How are phagocytes attracted towards the pathogen in phagocytosis?	Chemical products of the pathogen act as attractants
What happens after the pathogen is attached to the phagocyte?	The phagocyte ingulfs it
What is the name of the vesicle in which the pathogen is engulfed in?	A phagosome
Which structures inside the phagocyte bind to the phagosome and release their contents?	Lysosomes
What is in the contents of the lysosomes and what do they do?	Enzymes - break down the pathogen by hydrolysis
What happens to the soluble products from the breakdown of the pathogen?	They are absorbed into the cytoplasm of the phagocyte
Phagocytosis causes ___________ at the site of infection	Inflammation
The release of which chemical results in inflammation?	Histamine
What does histamine cause the blood vessels to do?	Dilate
What does this speed up?	The delivery of phagocytes to the site of infection
What are the two specific defence mechanisms?	Cell mediated response, humoral response
Which of the two involves T lymphocytes?	Cell mediated response
Which lymphocytes are involved in humoral immunity?	B lymphocytes
Which mechanism is immunity involving antibodies present in the bodily fluids?	Humoral
Cell mediated response using T lymphocytes involves which kind of cell?	Body cells
What do T cells respond to?	An organisms own cells that have been invaded by non-self material
How can T cells distinguish between invader cells and normal cells?	Phagocytes present antigens of pathogen on their own surface, virally invaded body cells present viral antigens on their cell surface membranes, cancer cells present antigens as a sign of distress
What name is given to these types of cell?	Antigen presenting cells
What helper T cells do to the antigens on the surface of the phagocyte?	Fit onto them
What does this activate?	Other T cells to divide rapidly and form clones
What are the 4 things the cloned cells can do?	1. Develop into memory cells 2. Stimulate phagocytosis 3. Stimulate B cells to divide 4. Kill infected cells
Which part of the T helper cells fit on to the antigen?	The specific receptor
What do killer T cells produce and how does it kill infected cells?	A protein - makes holes in the cell surface membrane; cell becomes freely permeable and dies as a result
Which type of pathogen are T cells especially effective against and why?	Viruses - they live and reproduce inside body cells
Where do T lymphocytes mature?	The thymus gland
Where do B lymphocytes mature?	Bone marrow
What is 'humor' another word for?	Bodily fluids
What do B cells produce?	Antibodies
What happens when a specific antibody attaches to an antigen in the blood?	The type of B cell that produces it divides rapidly by mitosis
This forms clones. What do these clones all produce?	The antibody specific to the foreign antigen
In practice, what do most pathogens have on their surfaces?	Many different proteins
What do these all act as?	Antigens
What other substances act as antigens?	Toxins
Give an example of a pathogen that releases a toxin	The pathogen that causes cholera - vibrio cholerae
What does mean regarding B cells?	Many different B cells will clone
What are the two types of cell the clones can develop in to?	Plasma cells and memory cells
Which out of the two secrete antibodies directly?	Plasma cells
How long to plasma cells survive?	A few days
Around how many antibodies can plasma cells produce every second?	2000
What do antibodies do?	Destroy the pathogen and any toxins it produces
Which stage of immune response are plasma cells therefore responsible for?	Primary immune response
How long to memory cells live for?	Decades
Memory cells circulate in the _______ and ______ _______	Blood and tissue fluid
What happens when memory cells encounter the same pathogen at a later date?	They divide rapidly and develop into plasma cells and more memory cells
What do the plasma cells do?	Produce antibodies to destroy the pathogen
What do the memory cells do?	Circulate in readiness for future infection
Which stage of the immune response are memory cells responsible for and why?	The secondary immune response - they are responsible for long term immunity
Why do people get flu more than once?	There are many different strains - the antigens of the virus are constantly changing
What name is given to this?	Antigenic variability
Why does the body treat every infection like a new one in terms of the influenza virus?	There will be no corresponding memory cells to stimulate the production of corresponding antibodies so the body undergoes the primary immune response
Why do we feel the symptoms of the flu each time we get it?	The primary response is much slower - in the meantime we develop the symptoms e.g sore throat, high temperature etc
What molecules are antibodies made up of?	Proteins
Why does this allow for a vast variety of antibodies?	Proteins occur in almost an infinite amount of forms
How many polypeptide chains are antibodies made of?	4
What are the two names given to the pairs of chains?	Heavy chains & light chains
When the antibody fits onto the antigen, what name is given to this structure?	The antigen-antibody complex
Why is the binding site called the 'variable region'?	Because it is different for each antibody
What name is given to the rest of the antibody that is the same for each one?	The constant region
Many pathogens have many different antigens on its surface. What will this induce when it enters the body?	Each antigen will induce a different B cell to multiply and clone
Collectively, what are the antibodies that these B cells known as?	Polyclonal antibodies
What is the same given to the antibodies that are isolated and cloned so there is just one type?	Monoclonal antibodies
How can monoclonal antibodies be used in cancer treatment?	They can attach to the cancer cells and activate a cytotoxic drug which kills the cancer cells
Why does this cause little, if any damage to other cells?	The cytotoxic drug is only activated by cells to which the monoclonal antibodies are attached i.e the cancer cells
Monoclonal antibodies can 'knock out' specific T cells - what is this useful for and why?	Transplant surgery - there is often rejection due to the action of T cells
Monoclonal antibodies can also be used to separate a chemical from a mixture and in immunoassay. What is immunoassay?	A method of calculating the amount of substance in a mixture
What is immunoassay used in?	Home pregnancy kits, testing for drugs in the urine of athletes
What were the 2 main struggles with trying to produce monoclonal antibodies?	B cells are short lived and only divide inside a living organism
When producing monoclonal antibodies, which animal is exposed to the non self material?	A mouse
What do the B cells in the mouse then do?	Produce a mixture of antibodies (polyclonal antibodies)
What type of cells are the B cells of the mouse mixed with to enable them to divide outside the body?	Cancer cells
Why is this?	Because cancer cells divide rapidly outside the body
Why is detergent added to the mixture of B cells and cancer cells?	To break down the cell-surface membranes and enable them to fuse together
How are clones of each B cell made from this?	They are separated under a microscope and cultured to form a group (clone)
What is each clone tested to see?	Whether it is producing the required antibody
What is done to the clones producing the required antibody?	They are grown on a large scale
Why are they called 'monoclonal' antibodies?	Because they come from a single B cell
What is the name given to the process in which the antibodies are modified so that they work in a human?	Humanisation
Why is this necessary?	Monoclonal antibodies from a mouse will be recognised as 'non-self' and destroyed by human antibodies
Why is the use of mice in producing monoclonal antibodies an ethical issue?	It involves giving mice cancer
Genetic engineering is often brought up in debate when discussing the production of monoclonal antibodies. Why is this?	To eliminate the need for humanisation, transgenic mice can be used (giving mice a human gene so they produce human antibodies rather than mouse ones)
What diseases have monoclonal antibodies been successful in treating?	Cancer, diabetes
However there have been deaths associated with the use of monoclonal antibodies when treating ________	Multiple sclerosis
What is active immunity?	When an individual is exposed to a pathogen and becomes immune by producing their own antibodies in response.
What is passive immunity?	Immunity by the introduction of the antibodies from an outside source - can be induced by a vaccine
What are 4 features of a successful vaccination programme?	Few side effects - must be sufficient quantities to immunise the entire vulnerable population - must be means of producing, transporting an storing the vaccine available - trained staff
A vaccination might not eliminate a disease. Why is this? (5)	People may have defective immune systems - antigenic variability - objections to vaccination - people may harbour the pathogen and infect others - some pathogens 'hide' from immune defences
It is difficult to control cholera by vaccination. Cholera is an intestinal disease. Why does this make it difficult?	Any oral treatment is rapidly flushed by the diarrhoea, a symptom of cholera
What are two other factors that make cholera hard to control by vaccination?	Antigenic variability - mobile populations (due to war, tourism etc) spread the pathogen
Tuberculosis is another disease that is difficult to control by vaccination. There are 4 reasons why. What are these reasons?	Increase HIV = increase in defective immune systems; increase elderly population = increase in defective immune systems; many people in overcrowded accommodation; mobile populations

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