Author: Philip Colls
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Immune system Booklet revision questions     NAME:
Q1. (a)     Describe how phagocytosis of a virus leads to presentation of its antigens.
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(b)     Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen.
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(c)     Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints. Scientists have found a virus that produces a protein very similar to human collagen.
Suggest how the immune response to this viral protein can result in the development of RA.
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 (2)   (Total 8 marks)
Q2. (a)     What is a pathogen?
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(b)     When a pathogen enters the body it may be destroyed by phagocytosis.
Describe how.
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(c)     When a pathogen causes an infection, plasma cells secrete antibodies which destroy this pathogen.
Explain why these antibodies are only effective against a specific pathogen.
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(Total 7 marks)
Q3. (a)     When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how.

(5)
(b)     Describe the difference between active and passive immunity.

(5)
(Total 10 marks)
Q4. (a)     When a person is bitten by a venomous snake, the snake injects a toxin into the person. Antivenom is injected as treatment. Antivenom contains antibodies against the snake toxin. This treatment is an example of passive immunity.
Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity.
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(2)
The chart shows a procedure used to produce antivenom.

(b)     A mixture of venoms from several snakes of the same species is used.
Suggest why.
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(2)

(c)     Horses or rabbits can be used to produce antivenoms.
When taking blood to extract antibody, 13 cm^3 of blood is collected per kg of the animal’s body mass.
The mean mass of the horses used is 350 kg and the mean mass of the rabbits used is 2 kg
Using only this information, suggest which animal would be better for the production of antivenoms.
Use a calculation to support your answer.
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(d)     During the procedure shown in the chart the animals are under ongoing observation by a vet. Suggest one reason why.
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(e)     During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination programme.
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Q5.  (a)     Changes to the protein coat of the influenza virus cause antigenic variability. Explain how antigenic variability has caused some people to become infected more than once with influenza viruses.
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(2)
(b)     The drawings show the changes in a B lymphocyte after stimulation by specific antigens.
 
B lymphocyte before stimulation        B lymphocyte after stimulation
(i)      Describe the role of macrophages in stimulating B lymphocytes.
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(1)
(ii)     Explain how the changes shown in the drawings are related to the function of B lymphocytes.
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(4)     (Total 7 marks)
Q6.  The diagram shows a human immunodeficiency virus (HIV).
 
(a)     (i)      Name structure P and enzyme Q.
Structure P ____________________________________________________
Enzyme Q ___________________________________________________(2)
(ii)     What is the function of the RNA molecules in this virus?
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(b)     Describe how new viruses are produced after HIV has infected a T cell.
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Q7.
(a)     What is an antigen?
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(2)
(b)     Describe how B-lymphocytes respond when they are stimulated by antigens.
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(c)     The diagram shows some components of a human immunodeficiency virus (HIV).
 
(i)      Suggest which labelled component of the virus is most likely to act as an antigen. Give a reason for your answer.
Component ____________________________________________________
Reason _______________________________________________________
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(ii)     A cell that HIV infects is 15 µm in diameter. Calculate how many times larger in diameter this cell is than an HIV particle. Show your working.
 
Answer ____________________ times larger (2)                                            (Total 9 marks)
Q8. Nicotine is the addictive substance in tobacco. When nicotine reaches the brain, it binds to a specific protein. This causes the release of chemicals that give a feeling of reward to the smoker. This reward is part of the reason why people find it difficult to stop smoking.
Scientists have developed a vaccine against nicotine to help people stop smoking.
They set up an investigation, which involved a large number of volunteers. Once a month for 5 months, one group of volunteers was given the vaccine and the other group was given a placebo.
At regular intervals, the scientists measured the concentration of antibodies to nicotine in the blood of each group of volunteers. They also calculated the percentage of volunteers who had stopped smoking from months 2 to 6 of the investigation.
(a)     (i)      In this investigation, neither the volunteers nor the scientists knew if a particular volunteer was receiving the vaccine or a placebo.
Suggest two reasons why this made the scientists’ results more reliable.
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2. ____________________________________________________________
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(2)
(ii)     The scientists measured the concentration of nicotine in the blood of two volunteers who smoked the same number of cigarettes per day.
Suggest two reasons why the concentration of nicotine in the blood of these smokers might be different.
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(2)
(b)     (i)      Suggest how this vaccine could help people to stop smoking.
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(Extra space) ________________________________________________ (3)
(ii)     Some people have suggested that this vaccine should not be given free to smokers on the National Health Service (NHS). Evaluate this suggestion.
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The scientists measured the concentration of antibodies to nicotine in the blood of the volunteers for 12 months after the first vaccination. As a result of these measurements, they divided the volunteers who received the nicotine vaccine into three groups:
•        high antibody responders
•        medium antibody responders
•        low antibody responders.
The figure below shows their results.
The scientists also recorded the number of volunteers who had stopped smoking from months 2 to 6 of the investigation.
The table below shows these results.
 
Month when vaccine or placebo was given

Group

Percentage of volunteers
who had stopped smoking from
months 2 to 6 of the investigation

High antibody responders | 56.6
Low antibody responders | 38.1
Medium antibody responders | 32.1
Placebo | 31.3
(c)     A journalist reported that this vaccine is a major breakthrough in helping people to stop smoking. Do these data support this statement? Explain your answer.
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(5)
(Total 15 marks)

Q9. Scientists tested a claim that modified citrus pectin (MCP) increased the production of antibodies by the immune system.
•        They divided a large number of mice into five groups.
•        They gave the mice in each group a different amount of MCP in their food.
•        The scientists then stimulated antibody production in the mice. They did this by injecting them with a solution containing sheep red blood cells.
The results are shown in the graph.
 
(a)     The data obtained in this investigation have been plotted on a graph. How would you join the points? Give a reason for your answer.
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(b)     Use the graph to describe the effect of MCP on mean antibody production.
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(c)     Calculate the percentage increase in antibody production from when there was no MCP in the diet to when the dose is 1.0 g per kg.

 
 
Answer ____________________%
(2)
(d)     The dose of MCP given to the mice was calculated in g per kg body mass. Explain why the dose was calculated per unit mass.
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(1)
(e)     Explain how antibodies were produced when the mice were injected with sheep red blood cells.
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(3)
(f)      A newspaper suggested that these data show that taking MCP will give people increased resistance to disease. With reference to the data give two reasons why this conclusion may not be valid.
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(2)
(Total 11 marks)
Q10. The figure below shows a test that has been developed to find out if a person has antibodies to the human immunodeficiency virus (HIV) antigen.
 
Step 1 | HIV antigens are attached to a test well in a dish.

Step 2

A sample of blood plasma is added to the well.
If HIV antibodies are present, they bind to the HIV antigen.

Step 3

The well is washed.
A second antibody with an enzyme attached is then added.
This binds specifically to the HIV antibody.

Step 4

The well is washed again.
A yellow solution is added, which changes to blue if the enzyme is present. A blue colour shows that the person has HIV antibodies.

(a)     This test only detects the presence of HIV antibodies. Give two reasons why it cannot be used to find out if a person has AIDS.
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2. _________________________________________________________________
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(b)     The solution will remain yellow if a person is not infected with HIV. Explain why.
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(2)
(c)     A mother who was infected with HIV gave birth to a baby. The baby tested positive using this test. This does not prove the baby is infected with HIV.
Explain why.
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(2)
(d)     A control well is set up every time this test is used. This is treated in exactly the same way as the test wells, except that blood plasma is replaced by a salt solution.
Use information from the figure above to suggest two purposes of the control well.
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(2)
(Total 8 marks)

Mark schemes
Q1.
(a)     1.      Phagosome / vesicle fuses with lysosome;
2.      (Virus) destroyed by lysozymes / hydrolytic enzymes;
3.      Peptides / antigen (from virus) are displayed on the cell membrane;
1.      Accept vacuole fuses with lysosome
1.      Reject virus fuses with lysosome
3
(b)     1.      Helper T cell / TH cell binds to the antigen (on the antigen-presenting cell / phagocyte);
2.      This helper T / TH cell stimulates a specific B cell;
3.      B cell clones
OR
B cell divides by mitosis;
4.      (Forms) plasma cells that release antibodies;
1. and 2. ‘Helper’ is required once only.
2.      Accept ‘This (helper) T cell stimulates a competent B cell’
‘T cell stimulates B cell to undergo clonal selection’. This statement achieves mp2 and mp3.
3 max
(c)     1.      The antibody against virus (antigen) will bind to collagen;
2.      This results in the destruction of the (human) cells / collagen;
2.      Ignore ‘attacks’
2
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Q2.
(a)     (Micro)organism that causes disease / harm to body / an immune response;
Accept: named microorganism that causes disease
Allow infection
1
(b)     1.      Phagocyte attracted by a substance / recognises (foreign) antigen;
Accept named substance eg chemical / antigen
2.      (Pathogen)engulfed / ingested;
Accept: description
3.      Enclosed in vacuole / vesicle / phagosome;
4.      (Vacuole) fuses / joins with lysosome;
5.      Lysosome contains enzymes;
Accept named example of enzyme
6.      Pathogen digested / molecules hydrolysed;
Neutral: Destroyed
4 max
(c)     1.      Antigens (on pathogen) are a specific shape / have specific tertiary / 3D structure;
1 / 3 Structure alone is insufficient
2.      Antibody fits / binds / is complementary to antigen / antibody-antigen complex forms;
Reject - active site
OR
3.      Antibodies are a specific shape / have specific tertiary / 3D structure;
4.      Antigens (on pathogen) fit / bind / are complementary to antibody / antibody-antigen complex forms;
2
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Q3.
(a)     1.      Vaccine contains antigen from pathogen;
2.      Macrophage presents antigen on its surface;
3.      T cell with complementary receptor protein binds to antigen;
4.      T cell stimulates B cell;
5.      (With) complementary antibody on its surface;
6.      B cell secretes large amounts of antibody;
7.      B cell divides to form clone all secreting / producing same antibody.
5 max
(b)     1.      Active involves memory cells, passive does not;
2.      Active involves production of antibody by plasma cells / memory cells;
3.      Passive involves antibody introduced into body from outside / named source;
4.      Active long term, because antibody produced in response to antigen;
5.      Passive short term, because antibody (given) is broken down;
6.      Active (can) take time to develop / work, passive fast acting.
5 max
[10]
Q4.
(a)     1.      (Antivenom/Passive immunity) antibodies bind to the toxin/venom/antigen and (causes) its destruction;
For ‘bind’ accept ‘attach’, ignore ‘attack’.
For ‘destruction of toxin’ accept agglutination or phagocytosis.
Ignore reference to antibodies ‘neutralising toxin/stopping damage’
Reject reference to ‘killing’ toxin/venom.
2.      Active immunity would be too slow/slower;
Accept ‘passive immunity is faster’, not simply ‘passive immunity is fast’.
2
(b)     1.      May be different form of antigen/toxin (within one species)
OR
Snakes (within one species) may have different mutations/alleles;
2.      Different antibodies (needed in the antivenom)
OR
(Several) antibodies complementary (to several antigens);
No mark points are available for answers related to collecting venom from different species of snake.
2 max
(c)     1.      Horses because more antivenom/antibodies could be collected (as more blood collected);
2.      4550 (cm^3) v 26 (cm^3) (blood collected);
Accept 175 rabbits needed to (collect the volume of blood from) one horse.
2
(d)     1.      (So) the animal does not suffer from the venom/vaccine/toxin;
2.      (So) the animal does not suffer anaemia/does not suffer as a result of blood collection;
3.      (So) the animal does not have pathogen that could be transferred to humans;
Accept ‘To fulfil licence/legal requirements’.
Accept ‘(So) the animal does not have pathogen that could result in it producing other antibodies (not wanted in the antivenom)’.
For ‘pathogen’ accept correct form of pathogen.
1 max
(e)     1.      B cells specific to the venom reproduce by mitosis;
Accept in context of primary or secondary immune response.
Credit idea of specificity if given once in relation to T or B cell.
Accept a description for specificity.
Accept ‘clone’ for ‘reproduce by mitosis’.
‘Clonal selection of B cells’ = MP1.
2.      (B cells produce) plasma cells and memory cells;
3.      The second dose produces antibodies (in secondary immune response) in higher concentration and quickly
OR
The first dose must be small so the animal is not killed;
Accept ‘a lot of antibody’ for ‘higher concentration of antibody’.
3
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Q5.
(a)     memory B / T cells do not recognise (new antigens);
antibodies previously produced are not effective
as shape not complementary to new antigen;
2
(b)     (i)      antigen in membrane presented to lymphocytes / 
produce cytokinins;
1
(ii)     mitochondria provide (more) ATP / energy;
(more) RER / ribosomes synthesise proteins;
(more) Golgi body secretes / modifies or packages proteins / 
produces glycoproteins;
(B lymphocytes) produces antibodies;
4
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Q6.
(a)     (i)      P = membrane / lipid envelope / phospholipid bilayer;
Q = reverse transcriptase;
Accept (host) cell membrane;
2
(ii)     Carries genetic information / to make DNA;
Q Do not accept ‘information’ on its own
Accept genes, alleles,
to make (viral) protein;
1
(b)     DNA copy made (of viral RNA);
Inserted into host DNA / chromosomes;
(Uses viral DNA to) make viral proteins/particles;
Makes viral RNA;
(Host) cell makes new viruses;
“Budding off” / wrapped in cell membrane;
Accept reverse transcriptase makes DNA for 2 marks in correct context;
3 max
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Q7.
(a)     molecule / part of molecule / protein / glycoprotein / named molecule;
that stimulates an immune response / eq;
2
(b)     divide by mitosis / form clones; produce plasma cells; (plasma cells) 
make antibodies;
(plasma cells) produce memory cells;
4
(c)     (i)      glycoprotein AND
different shape to body proteins / RNA and reverse transcriptase
inside virus / phospholipids same as body’s / on the surface
of the virus;
1
(ii)     187.5;;
Accept 187 – 188
1 mark for HIV = 80nm;
2 max
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Q8.
(a)     (i)      1.      (Scientists) can't show bias / influence / may have a vested 
          interest / work for the company developing the vaccine;
Relates to the scientists
2.      (Volunteers) can't show psychological / mental effects / ‘placebo effect’ / expectations;
Relates to the volunteers
Accept: reduces the ‘Hawthorne effect’ / demand characteristics
Neutral: so they have no idea what they are taking
2
(ii)     Any two suitable suggestions, eg
Neutral: refs. to age and health
1.      Amount of nicotine in cigarettes;
Neutral: different types of cigarette / different ways / frequency of smoking
2.      Amount inhaled / absorbed / time since last cigarette;
Neutral: absorption by gut / digestion
Accept: absorption by mouth
3.      (Different) amounts excreted / metabolism / rate of binding (of nicotine) to protein;
Accept: broken down (differently)
4.      (Different) blood volumes;
Neutral: different body masses
5.      Nicotine from passive smoking / other smokers / other sources;
6.      Some volunteers received the vaccine / placebo;
Accept: some volunteers would have / would not have the antibodies
2 max
(b)     (i)      1.      Antibodies to nicotine produced / antibodies bind to nicotine;
Q Reject: vaccine contains / produces antibodies
Q Neutral: antibodies digest / kill / fight nicotine
2.      (So) nicotine does not bind to protein / does not reach the brain;
Q Reject: any reference to ‘active site’
Neutral: idea that the antibodies bind to the protein
3.      (So) cigarettes / smoking does not satisfy addiction / reward smokers / release (reward) chemicals;
3
(ii)     (Agree):
1.      People choose to smoke / know the risks;
2.      Should spend this money on education / preventing people from starting to smoke / treating other health problems / vaccines are expensive;
(Disagree):
3.      Unethical not to treat;
4.      Less money needed to treat the effects of smoking / cancer / smokers pay taxes so are entitled to treatment;
3 max
(c)     1.      High antibody responders have a high % to stop smoking / are more likely to stop smoking;
‘People producing a high concentration of antibodies’ is equivalent to ‘high antibody responders’
Accept: reference to values from the table
2.      Only a few may be high antibody responders / no numbers on how many are high / medium / low antibody responders;
Neutral: not all people are high antibody responders
3.      Percentage who stopped smoking is similar for placebo group and low / medium responders / some / % of placebo group (still) stopped smoking / placebo has the lowest value / % to stop smoking;
Accept: reference to values from the table
4.      Large sample size / double blind so reliable / representative;
5.      Antibody levels peak at / drop after 5 months / boosters may be needed at / after 5 months;
6.      May start smoking again after 5 / 6 months / do not know the percentage who stopped smoking after 5 / 6 months;
7.      Nicotine is not the only factor responsible for making people smoke;
Must mention nicotine
Do not accept: correlation does not mean causation / could be due to other factors
5 max
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Q9.
(a)     Straight lines point to point as not possible to predict intermediate values / values between points;
1
(b)     Increases then levels / falls;
Maximum antibody production 180 units / at dose of 0.25 g per kg;
2
(c)     Two marks for correct answer of 57.14 / 57.1;;
One mark for incorrect answer in which candidate clearly divides difference in antibody production / 60 by 105;
2
(d)     Takes into account different masses of mice / allows comparison;
Accept different weights of mice.
Do not accept different size.
1
(e)     Sheep red blood cells have antigens (on their surface);
Antigens are proteins foreign to mice / are non-self;
Stimulate B cells to produce antibodies;
3
(f)     Response only observed in mice;
Disease organisms not investigated;
Not all disease caused by pathogens / cured by antibodies;
i.e. not tested on humans
2 max
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Q10.
(a)     (To diagnose AIDS, need to look for / at)
1.      (AIDS-related) symptoms;
2.      Number of helper T cells.
Neutral: ‘only detects HIV antibodies’ as given in the question stem
2
(b)     1.      HIV antibody is not present;
Accept HIV antibodies will not bind (to antigen)
2.      (So) second antibody / enzyme will not bind / is not present.
2
(c)     1.      Children receive (HIV) antibodies from their mothers / maternal antibodies;
2.      (So) solution will always turn blue / will always test positive (before 18 months).
Allow 1 mark for the suggestion that the child does not produce antibodies yet so test may be negative
2
(d)     (Shows that)
1.      Only the enzyme / nothing else is causing a colour change;
2.      Washing is effective / all unbound antibody is washed away.
2
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