The shape of the lesson
By the end of the lesson, learners can
- Antigens and complementary antibodies: Extended.
- Infection, vaccination and memory: Extended.
- Vaccination protects the population: Extended.
- Antigen = specific shape on the pathogen. Antibody = protein with a complementary shape.
- Antibodies destroy pathogens directly or mark them for phagocytes.
- Active immunity: your own antibodies, after infection or vaccination; memory cells, long-term.
- Passive immunity: antibodies from another individual (placenta, breast milk); no memory cells, short-term.
One picture every idea returns to
Extended: active immunity is defence against a pathogen by antibody production in the body. Each pathogen has its own antigens with specific shapes, and specific antibodies are proteins with complementary shapes that bind to them, leading to direct destruction of the pathogen or marking it for destruction by phagocytes. Active immunity follows infection or vaccination and produces memory cells for long-term protection. Passive immunity is short-term: antibodies come from another individual (across the placenta, in breast milk) and no memory cells are made.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, A lock, a key, and a memory.. Every pathogen carries its own antigens, each with a specific shape. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: Antigens and complementary antibodies | Extended. Project tab 3 of the lab (Antigens and antibodies) and let a student drive it while the class predicts. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Infection, vaccination and memory | Extended. Project tab 4 of the lab (Vaccination, memory cells and passive immunity) and let a student drive it while the class predicts. | Pairs |
| 21 to 30 min | Teach and check: Vaccination protects the population | Extended. Project tab 5 of the lab (Vaccination and the spread of disease) and let a student drive it while the class predicts. | Corners |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 22 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Vaccination protects the population, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Corners
Put one answer or viewpoint in each corner of the room. Students move to the corner they agree with, justify the choice to a partner there, then hear one voice from each corner before the reveal.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Say the antibody has a complementary shape to the antigen, not "the same shape". | And antibodies are made by lymphocytes; phagocytes engulf pathogens but do not make antibodies. |
| Passive immunity gives no memory cells. | Do not say breast milk "gives the baby memory cells" or long-term immunity; the antibodies work at once but only for a short time. |
| Herd protection depends on the proportion of the population vaccinated. | If too few are vaccinated the disease still spreads through the unvaccinated people. |
Antibodies and vaccination: worksheet
6 questions, 22 marks. Written in the style of the papers; no past paper question is reproduced.
Extended. Outline the process of vaccination.
Extended. Explain how antibodies help to destroy a pathogen, and why an antibody made against one pathogen does not protect against a different one.
Extended. The antibody level in a person's blood was measured after two exposures to the same pathogen.
| First exposure | Second exposure | |
|---|---|---|
| Days until antibodies are detected | 7 | 2 |
| Peak antibody level / arbitrary units | 15 | 120 |
| Became ill? | yes | no |
(a) Calculate how many times greater the peak was after the second exposure. (b) Explain the differences in the response.
Extended. In a town, the percentage of children vaccinated against measles fell from 95% to 70% over ten years, and cases of measles rose sharply. Explain why, including why some children who were vaccinated may be put at risk.
Extended. Explain the importance of breast-feeding for the development of passive immunity in infants.
Extended. Compare active immunity and passive immunity. Give two similarities or differences in each of: the source of the antibodies, and how long protection lasts.
Answer key and marking notes
- Weakened pathogens, or their antigens, are put into the body.
- The antigens stimulate an immune response by lymphocytes, which produce antibodies.
- Memory cells are produced that give long-term immunity.
- Antibodies are proteins made by lymphocytes that bind to antigens on the pathogen.
- Binding leads to direct destruction of the pathogen, or marks it (and clumps pathogens together) for destruction by phagocytes.
- Each pathogen has its own antigens with specific shapes.
- An antibody has a shape complementary to only one antigen, so it cannot bind to the antigens of a different pathogen.
- (a) 120 ÷ 15 = 8 times greater.
- (b) After the first exposure only a few lymphocytes had the right shape, so antibody production was slow and the pathogen multiplied, causing illness.
- Memory cells were made during the first response.
- On second exposure the memory cells recognised the antigen at once, so antibodies were made sooner and in much larger amounts, destroying the pathogen before illness.
- Vaccinated children have memory cells, so they do not become ill or pass the virus on.
- At 95% an infected child rarely meets an unvaccinated child, so chains of transmission break and the disease cannot spread.
- At 70% many more children can catch and pass on the virus, so outbreaks spread through the unvaccinated.
- People who cannot be vaccinated (very young babies, people who are ill) are no longer protected by the vaccinated majority; and a few vaccinated people may not have made a full response.
- Breast milk contains antibodies made by the mother.
- These give the infant immediate protection against pathogens the mother has met, while its own immune system is still developing.
- This is passive immunity: it is short-term, because no memory cells are made and the antibodies are gradually broken down.
- Both involve antibodies that bind to specific antigens on a pathogen.
- Active: antibodies are made by the person's own lymphocytes, after infection or vaccination.
- Passive: antibodies are acquired from another individual, for example across the placenta or in breast milk.
- Active immunity is long-term because memory cells are made; passive immunity is short-term because no memory cells are made.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which type of cell produces antibodies?
- ALymphocyte
- BPhagocyte
- CRed blood cell
- DPlatelet
How does a phagocyte destroy a bacterium?
- AIt engulfs the bacterium and digests it
- BIt makes antibodies that dissolve the bacterium
- CIt releases a toxin that poisons the bacterium
- DIt secretes acid that kills the bacterium
Extended: which statement about antigens is correct?
- AEach pathogen has its own antigens, which have specific shapes
- BAntigens are proteins made by lymphocytes to destroy pathogens
- CAll pathogens share the same antigens, so one antibody fits all
- DAntigens are made by memory cells after a vaccination
Extended: what does a vaccine put into the body?
- AWeakened pathogens or their antigens
- BReady-made antibodies against the pathogen
- CMemory cells taken from an immune person
- DAntibiotics that kill the pathogen
Extended: the graph shows the antibody concentration in a person's blood after two exposures to the same antigen, on day 0 and day 40. Which statement explains the difference between the two responses?
- AMemory cells from the first exposure made the second response faster and larger
- BAntibodies from the first exposure stayed at a high level until day 40
- CThe second dose contained far more antigen than the first dose
- DPhagocytes learned to make antibodies after the first exposure
Extended: which of these gives a person long-term immunity to a disease?
- ARecovering from an infection by the pathogen
- BReceiving antibodies in breast milk as a baby
- CReceiving antibodies across the placenta before birth
- DAn injection of antibodies made in another person
Extended: a city has 12 000 children. 85% of them are vaccinated against measles. How many children are not vaccinated?
- A1800
- B10 200
- C1200
- D180
Extended: a breast-fed baby is protected against a disease its mother had, but only for a few months. Why does the protection not last?
- AThe antibodies are broken down and no memory cells were made
- BThe baby's memory cells die once breast-feeding stops
- CThe baby's lymphocytes destroy the mother's antigens
- DBreast milk contains weakened pathogens that soon die
Quiz key
Lymphocytes are white blood cells that produce antibodies. Phagocytes are white blood cells too, but they engulf and digest pathogens rather than making antibodies. Red blood cells carry oxygen. Platelets help blood to clot.
A phagocyte engulfs the bacterium, taking it into the cell, and digests it with enzymes. Antibodies are made by lymphocytes, not phagocytes. Toxins are made by some bacteria, not by our white blood cells. Acid that kills pathogens is made in the stomach.
Each pathogen has its own antigens, molecules with specific shapes, and this is why immunity is specific. Proteins made by lymphocytes are antibodies, not antigens. Different pathogens have antigens of different shapes, so one antibody cannot fit all. Memory cells are lymphocytes that remember an antigen; they do not make antigens.
A vaccine contains weakened pathogens or their antigens, which stimulate lymphocytes to make antibodies and memory cells: active immunity. Ready-made antibodies would give only passive, short-term immunity with no memory cells. Memory cells are made by the vaccinated person's own body, not injected. Antibiotics treat bacterial infections and give no immunity.
The first exposure produced memory cells. On the second exposure they recognise the antigen at once, so antibodies appear after a shorter delay and reach a much higher concentration. The graph shows the antibody level had fallen almost to zero by day 40, so the antibodies themselves did not last. Nothing suggests a bigger dose; the faster, larger response is typical of a secondary response. Phagocytes never make antibodies; lymphocytes do.
After an infection the person's own lymphocytes made antibodies and memory cells, so this is active immunity and is long-term. Antibodies in breast milk, across the placenta or injected from another person are all passive immunity: the antibodies come from another individual, no memory cells are made, and protection is short-term.
100% − 85% = 15% are not vaccinated, and 15% of 12 000 = 0.15 × 12 000 = 1800. 10 200 is the number who are vaccinated. 1200 is 10% of 12 000, using the wrong percentage. 180 comes from a decimal slip, using 0.015 instead of 0.15.
This is passive immunity: the antibodies came from the mother. They are gradually broken down, and because the baby's own lymphocytes did not respond, no memory cells were made, so the protection is short-term. The baby has no memory cells for this disease to lose. Breast milk passes on the mother's antibodies, not her antigens or weakened pathogens.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.