10.1.3B5. Transport in Humans
Active Immunity — Combined Science 0653 - Biology Revision Notes & Topical Questions
5 min read 7 parts Lesson 15 of 15 Unit quiz
Section 1 of 7What active immunity is (HT only)
Definition
- Definition Active immunity is protection gained when your own body makes antibodies against a pathogen and forms memory cells.
- 'Active' means your immune system does the work itself.
Memory cells
- Memory cells Memory cells are lymphocytes that stay in the body after an infection and keep the information needed to make the correct antibody.
Section 2 of 7Two ways to gain active immunity
| Route | What happens | Does the person get ill? |
|---|---|---|
| Natural infection | The person is infected by a pathogen and lymphocytes make specific antibodies and memory cells. | Yes, usually, because the pathogen multiplies before the response is strong enough. |
| Vaccination | A harmless form of the pathogen, such as a weakened or dead one, is introduced, which stimulates antibody production and memory cells. | Not normally, because the vaccine cannot cause the disease. |
Section 3 of 7Response after vaccination
1
The vaccine contains antigens from the pathogen but is harmless.
2
Lymphocytes recognise the antigens as foreign and produce antibodies that match them.
3
Some of these lymphocytes become memory cells that stay in the blood.
4
If the real pathogen later invades, memory cells respond very quickly, producing large numbers of antibodies before the pathogen can multiply and cause illness.
Section 4 of 7Features of active immunity
Active immunity
Slow acting
- Slow acting The first response takes days because lymphocytes must be selected and start making antibodies.
Long lasting
- Long lasting Memory cells remain, so protection can last for years or even for life.
Specific
- Specific The antibodies made match only one type of pathogen, so each disease needs its own immunity.
Section 5 of 7Comparing first and later responses
| Feature | First exposure | Later exposure to the same pathogen |
|---|---|---|
| Speed of antibody production | Slow, taking several days | Fast, within hours |
| Amount of antibody | Small at first | Large quantities |
| Memory cells | Formed during the response | Already present, and more are made |
| Illness | Likely with natural infection | Unlikely, because the pathogen is destroyed early |
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Active immunity | Immunity gained when the body makes its own antibodies after infection or vaccination. |
| Vaccination | Giving a harmless form of a pathogen to produce immunity without causing disease. |
| Memory cell | A long-lived lymphocyte that allows a fast response to a pathogen met before. |
| Lymphocyte | A type of white blood cell that produces antibodies. |
| Antibody | A protein that binds to a specific antigen on a pathogen. |
Section 7 of 7Exam technique
1
Saying vaccination gives you the antibodies. It makes your body produce them.
2
Describing active immunity as quick. It is slow to start but lasts a long time.
3
Forgetting memory cells when explaining why a second infection is milder.
4
Writing that a vaccine contains the active, disease-causing pathogen. It is dead, weakened or only part of it.
5
Assuming immunity to one disease protects against all others. Antibodies are specific.
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