monoclonal antibodies exam q corrections

Monoclonal antibodies (mAbs) are usually made using mouse lymphocytes.

Candida albicans infection produces serious symptoms in patients with a poor

immune system.

Recently scientists have produced mAbs to Candida albicans using human

lymphocytes produced naturally after an infection.

(a) Candida albicans lives in the throat of infected patients.

A sample is taken from the throat of a patient with a suspected Candida

albicans infection.

The sample is transferred onto a microscope slide.

Describe how the mAbs and a fluorescent dye could be used to see any

Candida albicans pathogens on the slide.

bind fluorescent dye to mAbs

1

put (bound) fluorescent mAbs on the slide (and rinse off)

ignore add mAbs and dye to slide

(unbound)

1

mAbs will bind to Candida albicans / pathogens and show up under

the microscope

allow mAbs will bind to Candida

albicans / pathogens and show up

under UV (lamp)

In a laboratory the human lymphocyte mAbs were injected into animals infected with Candida albicans.

The mAbs caused increased phagocytosis of the Candida albicans pathogens.

Doctors intend to start a trial to give the mAbs to patients severely ill with Candida albicans.

(b) Explain how increased phagocytosis of the Candida albicans pathogen will

help the patient.

more Candida albicans / pathogens will be engulfed / killed by phagocytes /

white blood cells

allow Candida albicans / pathogens will

be engulfed / killed by phagocytes /

white blood cells more quickly

do not accept white blood cells produce

antibodies

do not accept lymphocytes engulf

Candida albicans

1

therefore less damage to cells / tissues / organs

ignore less toxin released (by Candida

albicans)

A virus called RSV causes severe respiratory disease.

(a) Suggest two precautions that a person with RSV could take to reduce the

spread of the virus to other people.

any two from:

• regular hand washing

or

use hand sanitiser / alcohol gel

• cover nose / mouth when coughing / sneezing

allow wear a face mask

• put used tissues (straight) in the bin

• don’t kiss uninfected people

allow isolate patient from others

or

don’t share cutlery / cups / drinks with uninfected people

• clean / disinfect / sterilise surfaces regularly

ignore responses referring to infected people

Scientists have also used human lymphocytes to make mAbs to other

pathogens and to some types of cancer cells.

Suggest one reason why these new mAbs have been more successful in

treating diseases in humans than mAbs made using mice.

any one from:

• (the body will) not reject the mAbs

or (the body is) less likely to reject the mAbs

do not accept idea of rejection of cells

• mouse mAbs are (more likely to be) rejected

• the human lymphocytes have already responded to that

infection / cancer cell so they are known to work against the

disease

A trial was carried out to assess the effectiveness of using monoclonal

antibodies to treat patients with RSV.

Some patients were given a placebo.

(d) Why were some patients given a placebo?

as a control

or

to see / compare the effects of the treatment (vs. no treatment)

Evaluate how well the data in the table above supports the conclusion:

‘monoclonal antibodies are more effective at treating RSV than a

placebo’

(supports the conclusion because)

over double the number / % of patients (in the trial) were hospitalised with

the placebo (compared to MAB)

(does not support the conclusion because)

no information on patients not hospitalised / still unwell at home

or

other factors may have affected those admitted to hospital

allow correct named factor e.g. age / gender / other

illness

or

don’t know if it was a double blind trial

Figure 2 shows the parts of a pregnancy test strip.

The pregnancy test strip will show a positive test result when a woman is

pregnant.

Explain how the pregnancy test strip works to show a positive result.

(as) urine passes through reaction zone

HCG hormone binds to the mobile HCG antibody (in the reaction zone)

(passes up the stick) HCG hormone binds to the immobilised HCG

antibodies in the results zone

(the other) antibodies which do not attach to HCG

bind to antibodies in control zone

blue dye appears in both control and results zones (to show positive result)