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7. Immunity and Vaccination 1. The flow chart summarises the response of lymphocytes in- the blood to a bacterial infection. Bacterium enters bloodstream Bacterium detected by lymphocytes Clothing of lymphocytes by mitosis Plasma cells secrete antibody (a) Memory cells remain in lymph nodes Explain what is meant by the term antibody. ……………………………………………….……………………………………… ……………………………………………….……………………………………… (1) (b) Suggest why the cloning of lymphocytes by mitosis is important in the production of an antibody. ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… (2) (c) The process shown in the flow chart would lead to active immunity Explain how active immunity differs from passive immunity. ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… ……………………………………………….……………………………………… (3) (Total 6 marks) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 1 1 7. Immunity and Vaccination 2. (a) Explain the meaning of the term pathogen. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Explain how each of the following reduces the chances of pathogens causing disease. (i) Inflammation ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) (ii) Lysozyme ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (iii) Interferon ........................................................................................................................... ........................................................................................................................... (1) (Total 8 marks) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 2 2 7. Immunity and Vaccination 3. Children are vaccinated against a number of diseases. A vaccine contains disease-causing organisms which have been made harmless but which act as antigens. In order to achieve full protection, it is often necessary to give two injections of a vaccine. The graph below shows the change in the level of antibodies in the body following two injections of a vaccine against a disease. Antibody level / arbitrary units 6 5 4 3 2 1 0 0 First injection (a) (i) 2 4 6 8 10 Time / weeks Second injection Compare the changes in the level of antibodies in the body following the first and second injections of the vaccine. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (ii) Explain how vaccination can bring about an increase in the level of antibodies. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (b) Explain how passive immunity differs from active immunity. .............................................................................................................................................. .............................................................................................................................................. A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 3 3 7. Immunity and Vaccination .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (3) (c) Antibodies are just one of the many types of protein found in blood plasma. The table below shows the protein content of lymph, tissue fluid and blood plasma. Protein content/g dm–3 Lymph 26 Tissue fluid 19 Blood plasma 69 Compare the protein content of lymph with that of tissue fluid and blood plasma and suggest a reason for the differences. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (2) (Total 11 marks) 4. Dangerous blood clots in arteries, such as coronary arteries, can be dissolved by injecting streptokinase into the bloodstream. Streptokinase is an enzyme that rapidly digests blood clots. It is produced by bacteria and can be used as a treatment for patients with blocked arteries. The first treatment with streptokinase is much more effective than a second treatment. The graph below shows the concentration of anti-streptokinase antibodies in the blood following the first injection of streptokinase, and when streptokinase is injected again ten weeks later. 14 – 12 – 10 – Anti-streptokinase antibodies / arbitrary units 8– Second injection 6– 4– 2– 1 2 3 4 5 Time since injection / weeks – – – – – – – 0– 0 First injection 6 A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 4 4 7. Immunity and Vaccination (a) Streptokinase acts as an antigen when injected into the blood. Explain what is meant by an antigen. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) (i) With reference to the graph, compare the effects of the first and second injections on the concentration of antibodies in the blood over the first four weeks after injection. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) (ii) Explain the differences in the immune responses to the first and the second injections. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (4) (c) Suggest why the manufacturers of streptokinase recommend that it should not be used to treat a second blood clot in the same patient soon after the first treatment. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 5 5 7. Immunity and Vaccination (d) State why the injection of a different enzyme would not be affected by the response to streptokinase. ..................................................................................................................................... ..................................................................................................................................... (1) (Total 12 marks) 5. A new technique for vaccinating people involves injecting them with DNA. Viruses have proteins on their coats that are coded for by their DNA. The genes for producing viral proteins can be isolated and inserted into loops of DNA (plasmids). Plasmids can enter human cells which will then produce the viral proteins. The proteins will become part of the surface membrane of the human cell. The immune system will recognise these proteins as foreign and respond by producing antibodies and T killer cells. The process is summarised for one protein in the following diagram. Plasmid including gene from viral DNA Protein synthesis Cell in human body Nucleus Viral protein present on cell surface membrane Production of antibodies and T killer cells by immune system (a) Explain why the response of the immune system to the viral proteins is an example of active immunity. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 6 6 7. Immunity and Vaccination ..................................................................................................................................... ..................................................................................................................................... (2) (b) Explain how active immunity provides immunity against future infections by the virus. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) The table below compares the production and distribution of vaccines made using traditional methods with those made using DNA. DNA vaccine Traditional vaccine Time to develop vaccine against new strain of virus 2–3 weeks 4–6 months Time to produce enough doses for effective protection of population 2–3 months 2–3 years No special treatment Constant refrigeration Treatment during distribution Use the information in the table to suggest why the DNA vaccine is likely to be more effective at preventing the spread of a new strain of virus. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 7 7 7. Immunity and Vaccination (d) A traditional vaccine involves the injection of viral protein into the body. This usually stimulates the production of antibodies but not T killer cells. Suggest how the use of viral DNA might be more effective than viral protein in producing immunity to a virus. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (4) (Total 11 marks) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 8 8 7. Immunity and Vaccination 6. (a) Harmful bacteria are often present on the skin surface. Explain why these bacteria do not normally enter the body. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) The photograph below shows human skin which has been damaged by a cut. Dr. P. Marazzi/Science Photo Library Give two responses within the damaged skin which help to prevent bacteria entering the body. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) A2 Unit 4: The Natural Environment and Species Survival: Topic 6: Infection, immunity and forensics 9 9
