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| Frage | Antworten |
| 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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