Immunity (Edexcel International A Level Biology)

Rheumatoid arthritis is an inflammatory condition caused by the overactivity of the immune system.

The illustrations show the hand of a person with rheumatoid arthritis and the hand of a person without rheumatoid arthritis. The two images are shown to the same scale.

Give one piece of evidence, shown in the illustrations, that rheumatoid arthritis is an inflammatory condition.

(1)

(ii)

Give two other signs of inflammation that are experienced in the hand of a person with rheumatoid arthritis.

(1)

Tumour necrosis factor (TNF) is a protein that can be released by several types of cell. It plays an important part in the immune response.

This protein binds to specific receptors on the surface of cell membranes stimulating chemical reactions inside the cell. As a result, a number of responses may occur that include inflammation and the stimulation of phagocytosis by macrophages.

Antibodies to TNF are used to treat rheumatoid arthritis.

Scientists have used a virus that infects bacteria to produce antibodies to human TNF.

The diagram summarises this process.

Explain how attaching the gene for TNF to the viral gene results in TNF being displayed on the outside of the capsid.

(2)

(ii)

Explain why antibodies to TNF are used in the treatment of rheumatoid arthritis.

(2)

(iii)

Patients being treated with antibodies to TNF are more susceptible to tuberculosis (TB), which can be fatal.

Explain why patients being treated with antibodies to TNF can die from TB.

(4)

Humans can have one of four different blood types: A, B, AB or O.

Blood type is determined by antigens present on the membranes of red blood cells.

The table shows which antigens are present in each blood type.

Blood transfusions are used in the treatment of some diseases.

A blood transfusion involves taking blood from a healthy person and putting it into the person needing the treatment.

Which blood type can be used for all blood transfusions?

(1)

Explain what will happen if a person with blood type A is given a transfusion of blood type AB.

(4)

Bacteria live in our intestines (gut flora).

The membranes of cells lining our intestines have molecules similar to the antigens on red blood cells.

(i)

Explain why bacteria living in our intestines are important.

(2)

(ii)

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 living in our intestines secrete an enzyme that separates the sugars from the protein molecules.

Suggest why bacteria living in our intestines secrete this enzyme.

(2)

(iii)

Explain why this enzyme may be useful in blood transfusions.

(2)

In 2018, an organisation carried out a global survey into the attitudes of people towards vaccines.

Vaccines provide artificial active immunity.

Describe how a vaccine results in active immunity.

This survey included three aspects:

• The trust that people have in scientists
• Their thoughts on the safety of vaccines
• Their income.

The graph shows some of the results of this survey.

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 vaccination is more successful when a greater proportion of people are vaccinated.

Patients with cystic fibrosis may develop serious bacterial infections.

A patient with cystic fibrosis developed bacterial infections including Mycobacterium.

This patient was given a combination of antibiotics for several months.

Explain why a combination of antibiotics had to be given for several months.

(2)

(ii)

This patient did not respond to the combination of antibiotics, and later needed a lung transplant.

Suggest why this patient needed a lung transplant.

(3)

(iii)

Following the transplant, the patient was given immunosuppressive drugs.

Immunosuppressive drugs weaken the immune system. Some of these drugs work by preventing DNA synthesis in the patient.

As a result of the immunosuppressive drug treatment, the infection with Mycobacterium developed faster.

Explain why the infection with Mycobacterium developed faster when the patient was taking immunosuppressive drugs.

(4)

Phage therapy was used to treat the Mycobacterium infection in this patient.

Phages are viruses that target bacterial cells.

The graph shows how the number of Mycobacterium and the number of phages changed following the start of phage therapy.

Explain the changes in the number of bacteria and phages following the start of the phage therapy.

Use the information in the graph to support your answer.

The scientific document you have studied is adapted from an article in Education in Chemistry: Developing vaccines, Self-defence classes for our immune system.

Use the information from the scientific document and your own knowledge to answer the following questions.

The Ebola virus can infect endothelial cells.

Describe how this virus can cause internal bleeding (paragraph 1).

Explain how ‘our immune systems learn to make another type of protein, called an antibody’ (paragraph 4).

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 vaccine from the filter (paragraphs 8 and 9).

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 effective.

Scientists are using genetically modified bacteria and insect cells to produce the antigens for Ebola vaccines (paragraph 13).

Describe how insect cells could be genetically modified to produce the antigens for an Ebola vaccine. 

(4)

(ii)

Suggest three benefits of using an insect cell to produce the Ebola virus antigen.

Suggest why the stems of the different versions of haemagglutinin molecules are the same but the heads can be different (paragraph 15).

There are four types of immunity.

Artificial immunity develops when a person is immunised by an injection.

The table gives some statements about artificial immunity.

For each statement, put one cross ☒ in the appropriate box, in each row, to show which statements are correct for the types of artificial immunity.

Natural active immunity can develop when a person is infected with a virus.

(i)

Describe the role of macrophages in the development of natural active immunity to a virus, following infection.

(3)

(ii)

Explain why both T helper cells and T killer cells are needed in the immune response to a virus.

(4)

Human Immunodeficiency Virus (HIV) infects human cells, causing symptoms that may result in death.

Explain why the virus is an immunodeficiency virus.

A number of antiretroviral drugs are given to patients with HIV.

These include reverse transcriptase inhibitors and integrase inhibitors.

(i)

Explain how these two drugs reduce the development of HIV.

(2)

(ii)

These two drugs are often given in combination with other antiretroviral drugs.

Suggest why patients are given combinations of drugs.

(2)

(iii)

If a patient stops taking the antiretroviral drugs, the number of virus particles increases again.

Suggest why this increase occurs.

(2)

Pathogens continuously adapt to invade their host cells.

Host cells continuously adapt to avoid infection by pathogens.

This is an example of an ‘evolutionary race’.

The diagram shows the pathogen lambda phage (λ phage) attached to its host cell, E. coli.

How many of the following statements are correct for λ phage?

• the genetic material is DNA
• the capsid structure is described as complex
• the genetic material codes for the J protein

Describe the role of the λ phage J protein.

Use the information in the diagram to support your answer.

Maltoporin is coded for by the lamβ gene of E. coli.

Maltoporin is involved in the transport of some sugars into E. coli.

(i)

Give one reason why sugars are important to E. coli.

(1)

(ii)

Discuss how E. coli and λ phage could interact and develop in their evolutionary race for existence.

Use all the information in this question to support your answer.

(6)

The scientific document you have studied is adapted from an article in National Geographic: How personalized medicine is transforming your health care.

Use the information from the scientific document and your own knowledge to answer the following questions.

Explain what is meant by the phrase ‘gene variants’ (paragraph 4).

Explain why ‘tumours...riddled with different mutations’ are good candidates for immunotherapies (paragraph 6).

Explain why a CT scan was used to show that Judy Perkins was free of tumours (paragraph 10 and Figure 1).

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 immunotherapy used to treat Judy Perkins (paragraph 10).

Explain how ‘a gene variant that produces a defective form of an enzyme’ reduces the effectiveness of clopidogrel (paragraph 16).

Researchers have used stem cells to produce spinal cord tissue from individuals with amyotrophic lateral sclerosis.

These functioning tissues contain motor neurones and blood vessels.

Suggest why blood vessels are required to form functioning spinal cord tissue (paragraph 31).

Suggest how ‘a brew of growth factors and other proteins’ can stimulate induced pluripotent stem cells to produce a functioning tissue (paragraph 33).

When activated, T lymphocytes can divide rapidly and secrete proteins called cytokines.

These cytokines will activate different types of lymphocyte.

(1)

(1)

Describe the role of DNA polymerase in DNA replication during cell proliferation.

Explain how cytokine genes can be expressed in an activated T lymphocyte.

T lymphocytes produce different types of cytokine.

Some of these cytokines activate T killer cells and some activate B cells.

Explain why different cytokines can activate different cells.

CD45 is a protein found on the surface of lymphocytes. Different forms of the CD45 protein are found on the surface of different lymphocytes.

Describe how different forms of the CD45 protein can be produced from a single CD45 gene.