3.2 Monoclonal Antibodies

Monoclonal antibodies can be used in pregnancy tests. 

Antibodies specific to the HCG hormone detect HCG in the urine of pregnant women. 

Explain how pregnancy tests work. 

A similar process is used in lateral flow tests that test for Covid-19. 

These are tests that people can take at home and only take 20 minutes to identify if someone is infected with Covid-19 pathogens. 

Covid-19 is a virus that predominantly infects the nose, throat and lungs.

Explain how this technology could be altered to test for Covid-19 antigens instead of HCG. 

Sometimes when people take Covid-19 lateral flow tests they see a faint line in the 'test' region (see Test A in Figure 1). 

This is different to the bold line that is expected from a person who is infected with Covid-19 pathogens (see Test B in Figure 1). 

Both tests in Figure 1 show a positive result for someone being infected with Covid-19. 

Explain why both tests in Figure 1 are positive and suggest what causes the difference. 

Figure 1

Figure 2 compares the sensitivity of the lateral flow test with another test called the PCR test at different stages during an infection. 

PCR tests are carried out in a laboratory and results can take a few days to be returned. 

Figure 2

A researcher concluded from Figure 2 that PCR tests should be used rather than lateral flow tests.

Use this information and detail provided in part b) above to evaluate this conclusion.

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Monoclonal antibodies can be used to treat certain types of cancer. 

One of the ways they can do this is to trigger the body's own immune system to target the cancer cells and destroy them.

This works in a similar way to how the immune system destroys pathogens.

Explain how the immune system functions to destroy pathogens.

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When monoclonal antibodies destroy the cancer cells they are targeting the body's own cells.

Explain why this increases the risk of harmful side effects to the patients.

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Another immune response that can occur is in response to the monoclonal antibodies themselves. 

There are some instances where the body does not recognise the antibodies as human and it triggers the immune system to try and destroy them. 

Using your knowledge of how monoclonal antibodies are produced, suggest why this is the case. 

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This has been a stumbling block preventing the widespread use of monoclonal antibodies in a way that was predicted when they were first developed. 

Evaluate the use of monoclonal antibodies in medicine. 

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'Flu is caused by the influenza virus.

Outline the events that lead to viruses causing illness.

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There are precautions that a person can take to reduce the spread of viral infections.

Suggest two such precautions. 

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Severe disease of the breathing system is caused by a different virus, named RSV.

It is possible to treat an individual with an RSV infection by using monoclonal antibodies. 

Describe the process by which monoclonal antibodies against the RSV virus can be produced in the laboratory.

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Describe how monoclonal antibodies (mAbs) for RSV produce a therapeutic effect on a patient suffering with severe disease of the breathing system. 

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The monoclonal antibodies (mAbs) used to treat RSV are ineffective against the HIV virus.

Explain why.

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When monoclonal antibodies were first developed, it was hoped that they would be widely used to treat diseases like RSV. 

Give one reason why this is not yet the case. 

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Hepatitis B is one of the most infectious diseases.

The hepatitis B virus infects the liver.

A double-blind trial was carried out to assess the effectiveness of using monoclonal antibodies to treat patients with a hepatitis B infection.

Outline how a double-blind trial should be carried out.

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During the trial referred to in part (a), a number of patients were admitted to hospital because they felt unwell.

Information about these patients is shown in Table 1.

Table 1

Treatment	% of patients within each group admitted to hospital with hepatitis B
Group A: Placebo	6.2
Group B: Monoclonal antibody	1.8

3 000 patients were involved in the trial.

• Half the patients (Group A) were given the placebo
• Half the patients (Group B) were given the monoclonal antibody being tested

A scientist calculated that 48 patients were admitted to hospital with hepatitis B whilst the trial was in progress.

The scientist is incorrect.

Using the data in Table 1, calculate the actual number of patients admitted to hospital with hepatitis B during the trial. 

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Following on from the trial, a conclusion that 'the monoclonal antibodies are more effective at treating hepatitis B than the placebo' was suggested.

Evaluate how well the data in Table 1 support this conclusion. 

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HIV has caused millions of deaths over the last forty years.

The virus initially causes 'flu-like illness.

Late-stage HIV infection progresses to AIDS.

A person with AIDS is highly susceptible to infections.

Explain why.

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It is now possible to control a HIV infection with medication.

Diagnosing the cause of an infectious disease is necessary before doctors can prescribe the right course of treatment. 

Suggest why. 

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Monoclonal antibodies can be used to detect the HIV virus.

Explain what monoclonal antibodies are.

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State two other uses of monoclonal antibodies.

Monoclonal antibody test kits for HIV are readily available.

The first step in producing monoclonal antibodies involves isolating antigens present on the HIV virus.

Describe and explain how the antigen can be used to produce HIV monoclonal antibodies. 

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Monoclonal antibodies (mAbs) are traditionally produced using mouse lymphocytes, although recent advances in technology have allowed the same techniques to be used on human lymphocytes. 

A strain of the bacterium, Staphylococcus aureus, causes pneumonia by secreting a toxin into a patient's lung cells, causing them to become porous, which leads to loss of lung function. This kind of pneumonia is the most common cause of death of patients in intensive care units. 

A mAb has been developed to bind to the bacterial toxin, produced by S. aureus, and destroy it. The mAb is available in the form of a drug, referred to here as Drug X.

Table 1 shows the results of some early testing of the drug.

Table 1

Dosage of Drug X / mg	Deaths from pneumonia from Staphylococcus aureus / arbitrary units
0 (placebo)	75
400	43
5 000	33
7 000	32

Scientists concluded that the most appropriate dose of Drug X to give to patients should be 5 000 mg.

Use the data in Table 1 to evaluate their conclusion.

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Outline the steps that must be followed in order for Drug X to be deemed suitable to treat humans in a clinical trial. 

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Staphylococcus aureus lives in the lung tissues of infected patients and is present in their mucus.

A sample of the mucus is taken from the patient with a suspected Staphylococcus aureus infection. The sample can be transferred onto a microscope slide for examination.

Describe how mAbs and a fluorescent dye could be used to observe whether Staphylococcus aureus pathogens are present in the patient's mucus.