Infection and the immune response: Edexcel International A Level Biology questions

Every Edexcel International A Level Biology exam question on Infection and the immune response (specification points 6.7–6.12), 2019–2025, with its mark scheme and examiner’s report.

All 100 questions on Infection and the immune response, as a list

June 2025, Unit 4, Q2(a) (1 mark): Gut flora are important as they help protect the body from pathogens. State the meaning of the term pathogen. (1)
June 2025, Unit 4, Q5(a) (1 mark): Which types of immunity result in the production of antibodies? (1) A artificial active and natural active B artificial active and natural passive C artificial
June 2025, Unit 4, Q5(b)(i) (2 marks): Explain why a single antibody had to be made by the scientists. Use the information in the diagrams to support your answer. (2)
June 2025, Unit 4, Q5(b)(ii) (3 marks): Suggest how the scientists could make this single antibody. Use the information in the diagram to support your answer. (3)
June 2025, Unit 4, Q5(b)(iii) (2 marks): Explain how this single antibody helps the body destroy cancer cells. (2)
June 2025, Unit 5, Q8(e) (2 marks): Explain how an antibody could block the effects of an inflammatory signalling molecule (ISM) (paragraphs 7 and 8). (2)
January 2025, Unit 4, Q8(a) (2 marks): The diagram shows the distribution of cholera cases by age group and sex at birth in Malawi, in the first nine months of 2022. Key: females males 91 to 100 81 t
January 2025, Unit 4, Q8(b)(i) (2 marks): Describe suitable placebos for use in this clinical trial. Use the information in the question to support your answer. (2)
January 2025, Unit 4, Q8(b)(ii) (1 mark): The scientists running the trial concluded that a dose of 6 g of rice powder vaccine was needed to stimulate an immune response. State why they came to this con
January 2025, Unit 4, Q8(b)(iii) (2 marks): The scientists found that these antibodies also bind to different toxins produced by another type of bacteria. Explain why these antibodies, produced as a resul
January 2025, Unit 4, Q8(b)(iv) (3 marks): Some people in the clinical trial did not respond to the rice powder vaccine. The scientists determined the proportions of different types of bacteria (A, B, C,
January 2025, Unit 4, Q8(b)(v) (2 marks): Give two limitations when using this data to determine if the type of gut flora could cause a person to be a non‑responder to the vaccine. (2)
January 2025, Unit 4, Q9(c) (5 marks): In cancer cells, the viral envelope proteins are synthesised and incorporated into the cancer cell membrane. Explain why these viral envelope proteins could be
October 2024, Unit 4, Q3(a) (2 marks): Peptide fragments bind to MHC molecules to form an antigen‑MHC complex. This takes place in the rough endoplasmic reticulum (rER). The complex is then transport
October 2024, Unit 4, Q3(c) (2 marks): Explain why antigens need to be presented to T killer cells in a person’s immune response to viral infections. (2)
October 2024, Unit 4, Q3(d) (3 marks): Explain how the action of T killer cells results in a person recovering from a viral infection. (3)
October 2024, Unit 4, Q6(a)(i) (1 mark): Which is the proportion of the children under five in hospital who are under 6 months old? (1) 5 A 11 6 B 11 5 C 6 6 D 5
October 2024, Unit 4, Q6(a)(ii) (1 mark): Which would be a more appropriate scale to use on the y-axis so that the range of values for the number of deaths can be seen clearly? (1) A linear B logarithmi
October 2024, Unit 4, Q6(b) (2 marks): In one trial, people received a new vaccine against RSV. The results showed that this vaccine protected against two subtypes of RSV. Give two reasons why one va
October 2024, Unit 4, Q6(c)(i) (5 marks): As a result of passive immunity, the babies of these pregnant women were born with high levels of antibodies against RSV. Explain how passive immunity developed
October 2024, Unit 4, Q6(c)(ii) (3 marks): The scientists running this trial claimed that the vaccine was 85 % successful at protecting babies against RSV infections that required medical attention. Desc
October 2024, Unit 5, Q7(b)(ii) (2 marks): Explain how BVZ antibodies can cause the destruction of cancer cells. (2)
October 2024, Unit 5, Q8(i) (2 marks): Swelling is a symptom of inflammation. Explain why lecanemab may result in ‘brain swelling’ (Paragraph 35). (2)
October 2024, Unit 5, Q8(g) (2 marks): Describe what is meant by the term ‘monoclonal antibody’ (Paragraph 31). (2)
June 2024, Unit 4, Q5(c) (4 marks): Using a modified herpes simplex virus activates the immune system. Explain why activation of the immune system would result in destruction of the cancer cells.
January 2024, Unit 4, Q1(a) (1 mark): Which of the following also act as barriers, protecting the body from infection by bacteria? (1) A antigens and stomach acid B antigens and interferon C interfe
January 2024, Unit 4, Q1(b)(i) (2 marks): Describe two conclusions that can be made about the different methods of washing hands. (2)
January 2024, Unit 4, Q1(b)(ii) (2 marks): Explain the differences in the effects that these methods of washing hands have on the skin flora. (2)
January 2024, Unit 4, Q8(a) (2 marks): The table gives some statements about immunity. For each statement, put one cross in the appropriate box, in each row, to show whether these statements are true
January 2024, Unit 4, Q8(b) (2 marks): Vaccination against a virus results in the production of antibodies. Describe how antibodies are produced following activation of T cells. (2)
January 2024, Unit 4, Q8(c)(i) (2 marks): Explain two ways in which this investigation would have to be controlled to provide valid data. (2)
January 2024, Unit 4, Q8(c)(ii) (2 marks): In group 1, Vac 2 increased the levels of antibody more than Vac 1. Calculate how many times greater this increase was. (2) Answer
January 2024, Unit 4, Q8(c)(iii) (1 mark): Suggest why there is no data on the graph for group 1 before vaccination. (1)
January 2024, Unit 4, Q8(c)(iv) (6 marks): Explain the results of this investigation. (6)
October 2023, Unit 4, Q2(a)(i) (1 mark): Name the two other characteristics of inflammation. (1)
October 2023, Unit 4, Q2(a)(ii) (2 marks): Explain how heat helps the body respond to infection. (2)
October 2023, Unit 4, Q2(b) (2 marks): Describe how interferon helps the body respond to infection. (2)
October 2023, Unit 4, Q2(c) (3 marks): The immune response results in the production of antibodies following the first infection with a pathogen and on further infections with the same pathogen. The
October 2023, Unit 4, Q4(b)(i) (2 marks): The effect on the types of bacteria in the guts of babies fed on breast milk or another source of milk was investigated. The graph shows the proportion of five
October 2023, Unit 4, Q4(b)(ii) (2 marks): Explain the importance of healthy gut flora in preventing infection in a developing baby. (2)
October 2023, Unit 4, Q7(a) (2 marks): Suggest what the difference is between active immunotherapy and passive immunotherapy. (2)
October 2023, Unit 4, Q7(b)(ii) (4 marks): Some active anti‑cancer vaccines can contain the mRNA that codes for the neoantigens. Explain how vaccines containing the mRNA coding for neoantigens stimulate
October 2023, Unit 4, Q7(c) (2 marks): Monoclonal antibodies are made in a laboratory. Large numbers of identical antibodies specific to one type of antigen can be made. Explain how these antibodies
October 2023, Unit 4, Q7(d) (2 marks): In adoptive cell therapy, T cells are taken from the patient and large numbers of genetically identical cells are made in the laboratory. These cells are then i
October 2023, Unit 5, Q8(d) (3 marks): Explain how inflammation in the fascia is caused (paragraphs 8 and 9). (3)
June 2023, Unit 4, Q6(a) (1 mark): State the meaning of the term infection. (1)
June 2023, Unit 4, Q6(b)(i) (1 mark): Which is the approximate death rate from malaria in 2019? (1) A 1 in 180 B 1 in 600 C 1 in 1 800 D 1 in 6 000
June 2023, Unit 4, Q6(b)(ii) (1 mark): In 2019, 274 000 young children died from malaria. Which is the ratio of deaths in young children to deaths in other age groups? (1) A 0.7 : 1.0 B 1.0 : 0.5 C 1
June 2023, Unit 4, Q6(c)(i) (3 marks): Suggest why sporozoites are used in a vaccine against malaria. (3)
June 2023, Unit 4, Q6(c)(ii) (3 marks): In clinical trials of this vaccine, people were injected with the vaccine and two chemicals. One chemical kills sporozoites and the other kills merozoites. Dedu
June 2023, Unit 4, Q6(c)(iii) (3 marks): Later in the clinical trials, people were infected with one of two strains of sporozoites, three months after the vaccination. One strain was identical to the o
June 2023, Unit 5, Q8(c) (3 marks): “Microorganisms can also enhance the anti-tumor immune effect of drugs by promoting T cell accumulation and transformation.” Explain how microorganisms promote
January 2023, Unit 4, Q9(c)(i) (2 marks): The graph shows some of the results of this investigation. Uninfected, untreated macrophages Untreated macrophages infected with Mycobacterium tuberculosis Unin
January 2023, Unit 4, Q9(c)(ii) (4 marks): An ELISA is used to detect a specific antigen. The IL‑1β was detected using an ELISA. The diagram shows an ELISA. Step 2: container Step 4: container rinsed wit
October 2022, Unit 4, Q6(b)(i) (2 marks): Explain the phrase: ‘an antibody that is specific for ß‑amyloid’. (2)
October 2022, Unit 4, Q6(b)(ii) (3 marks): Drug ATD reduces the build-up of ß‑amyloid in the brains of people with Alzheimer’s disease. Suggest how drug ATD could result in the reduction of the build‑up
October 2022, Unit 4, Q6(c)(i) (2 marks): Suggest why this person did not have Alzheimer’s disease. (2)
October 2022, Unit 4, Q6(c)(ii) (2 marks): Explain why this drug could be produced only from B memory cells taken from a person who did not have Alzheimer’s disease. (2)
October 2022, Unit 5, Q7(a)(iii) (4 marks): Some patients receiving rHE develop anti-rHE antibodies. Describe how these antibodies may be produced. (4)
June 2022, Unit 4, Q3(a)(i) (2 marks): Describe how skin flora protect the body from infection. (2)
June 2022, Unit 4, Q3(a)(ii) (1 mark): Give one other way in which the skin protects the body from infection. (1)
June 2022, Unit 4, Q3(b)(i) (3 marks): Describe three conclusions that could be made from this graph. (3)
June 2022, Unit 4, Q3(b)(ii) (2 marks): Describe how this study should have been designed to collect valid data. (2)
June 2022, Unit 4, Q3(c)(i) (2 marks): Describe the role of macrophages in the non‑specific response of the body to these bacteria. (2)
June 2022, Unit 4, Q3(c)(ii) (2 marks): Describe the role of macrophages in the immune response of the body to these bacteria. (2)
June 2022, Unit 4, Q6(b)(v) (3 marks): Explain why this estimate would be lower if a vaccine for HIV became available in 2023. (3)
June 2022, Unit 5, Q8(h) (3 marks): Explain how the interaction of microbial and other factors could result in gastrointestinal inflammation such as IBD (Box 2). (3)
October 2021, Unit 4, Q3(a) (3 marks): Artificial immunity develops when a person is immunised by an injection. The table gives some statements about artificial immunity. For each statement, put one
October 2021, Unit 4, Q3(b)(i) (3 marks): Describe the role of macrophages in the development of natural active immunity to a virus, following infection. (3)
October 2021, Unit 4, Q3(b)(ii) (4 marks): Explain why both T helper cells and T killer cells are needed in the immune response to a virus. (4)
October 2021, Unit 5, Q6(d) (3 marks): T lymphocytes produce different types of cytokine. Some of these cytokines activate T killer cells and some activate B cells. Explain why different cytokines ca
October 2021, Unit 5, Q8(c) (4 marks): Suggest how the amyloid protein may prevent bacterial infection in the brain (paragraphs 7 and 22). (4)
October 2021, Unit 5, Q8(d) (4 marks): Explain how the bacterium Porphyromonas gingivalis that causes gum disease may invade the brain and cause inflammation in brain regions affected by Alzheimer’s
January 2021, Unit 4, Q1(a)(i) (2 marks): Complete the diagram to show the four characteristics of inflammation. (2) swelling Characteristics of inﬂammation
January 2021, Unit 4, Q1(a)(ii) (2 marks): Inflammation occurs following a cut to the skin. Describe the role of two of these characteristics of inflammation in response to a cut to the skin. (2)
January 2021, Unit 4, Q1(b)(i) (3 marks): The graph shows the effect of treating inflammation with curcumin extract and an anti-inflammatory drug, drug A. inﬂammation with no treatment Inﬂammation Key d
January 2021, Unit 4, Q1(b)(ii) (1 mark): Many treatments use 1 g curcumin extract. A sample of turmeric contains 3 % curcumin. Which is the mass of turmeric for one treatment? (1) A 0.03 g B 3.33 g C 3
January 2021, Unit 4, Q2(c)(i) (2 marks): Explain the role of gut flora in protecting the body from infection. (2)
January 2021, Unit 4, Q3(a) (4 marks): Describe how a vaccine results in active immunity. (4)
January 2021, Unit 4, Q3(b)(i) (3 marks): Identify three conclusions that can be drawn from the results of this survey. (3)
January 2021, Unit 4, Q3(b)(ii) (1 mark): Suggest one reason for the different attitudes of these people. (1)
January 2021, Unit 4, Q3(c) (2 marks): The more people in a population who are vaccinated against a disease, the less likely it is for non-vaccinated people to become infected. Suggest why vaccinatio
January 2021, Unit 5, Q8(b) (4 marks): Explain how ‘our immune systems learn to make another type of protein, called an antibody’ (paragraph 4). (4)
January 2021, Unit 5, Q8(c) (2 marks): One method of slowing the degradation of vaccine proteins is to dry a mixture of sugars and vaccine on a filter. Explain why flushing with water releases the va
January 2021, Unit 5, Q8(d) (3 marks): During the production of some vaccines, the virus is allowed to replicate in eggs (paragraph 13). Explain how a vaccine produced in this way may become less eff
October 2020, Unit 4, Q4(a)(i) (1 mark): Give one piece of evidence, shown in the photographs, that rheumatoid arthritis is an inflammatory condition. (1)
October 2020, Unit 4, Q4(a)(ii) (1 mark): Give two other signs of inflammation that are experienced in the hand of a person with rheumatoid arthritis. (1)
October 2020, Unit 4, Q4(b)(ii) (2 marks): Explain why antibodies to TNF are used in the treatment of rheumatoid arthritis. (2)
October 2020, Unit 4, Q4(b)(iii) (4 marks): Patients being treated with antibodies to TNF are more susceptible to tuberculosis (TB), which can be fatal. Explain why patients being treated with antibodies
October 2020, Unit 4, Q8(a)(i) (1 mark): Which blood type can be used for all blood transfusions? (1) A blood type A B blood type B C blood type AB D blood type O
October 2020, Unit 4, Q8(a)(ii) (4 marks): Explain what will happen if a person with blood type A is given a transfusion of blood type AB. (4)
October 2020, Unit 4, Q8(b)(i) (2 marks): Explain why bacteria living in our intestines are important. (2)
October 2020, Unit 4, Q8(b)(ii) (2 marks): Both the molecules on the membranes of the cells lining our intestines and the antigens on red blood cells have sugars attached to protein molecules. Bacteria l
October 2020, Unit 4, Q8(b)(iii) (2 marks): Explain why this enzyme may be useful in blood transfusions. (2)
October 2020, Unit 5, Q8(b) (4 marks): Explain why ‘tumors ... riddled with different mutations’ are good candidates for immunotherapies (paragraph 6). (4)
October 2020, Unit 5, Q8(d) (2 marks): Checkpoints are a type of protein that prevent the activation of immune cells. Explain why a checkpoint inhibitor was given with the lymphocytes in the immunoth
January 2020, Unit 4, Q8(a) (1 mark): Which row of the table shows the cells that present antigens to each of these T cells? (1) T helper cells T killer cells host-infected cells host-infected cells
January 2020, Unit 4, Q8(b)(ii) (2 marks): Explain why the CAR gene is inserted into the T cells in Step 3. (2)
January 2020, Unit 4, Q8(b)(iv) (3 marks): In Step 1, T cells are removed from a patient with cancer. Explain the advantages of injecting CAR-T cells into the same patient in Step 5. (3)
January 2020, Unit 4, Q8(b)(v) (2 marks): Currently, the use of CAR-T cells has been effective against blood cell cancers only. Suggest why CAR-T cells are not effective against cancer cells in solid tu

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