In active immunity the body makes its own antibodies and memory cells, while in passive immunity it receives antibodies made elsewhere. This decides how fast protection starts and how long it lasts.
This lesson follows explaining antigen-antibody responses. It shows why memory cells form in one case and not the other.
How do they differ on four features?
- Who makes the antibodies? Active: the person’s own lymphocytes. Passive: another source.
- Speed of protection. Active: slower, because the body must respond. Passive: immediate.
- Memory cells. Active: formed. Passive: not formed.
- Duration. Active: long. Passive: short.
Worked example: a written compare answer
Question: Compare active and passive immunity.
| Feature | Active immunity | Passive immunity |
|---|---|---|
| Antibodies made by | The person’s own lymphocytes | Another source, given ready-made |
| Start of protection | Takes time | Immediate |
| Memory cells | Formed | Not formed |
| Duration | Long | Short |
| Examples | After infection, after a vaccine | From the mother, from an antiserum |
Written answer: “In active immunity the body makes its own antibodies, whereas in passive immunity the antibodies come from another source. Active immunity is slower to start but lasts longer because memory cells form. Passive immunity starts at once but is short-lived because no memory cells form.”
The mistake that loses marks
The common slip is to say a vaccine gives passive immunity because the person did not catch the disease. But a vaccine introduces an antigen, so the body makes its own antibodies.
| Case | Who makes the antibodies? | Type |
|---|---|---|
| Vaccine containing an antigen | The person | Active |
| Antibodies passed from mother to baby before birth | The mother | Passive |
| Antiserum injection | Another source | Passive |
The fix is to ask “who made the antibodies?” before naming the type.
A routine for any case
- Ask who made the antibodies.
- If the person’s own lymphocytes did, it is active and memory cells form.
- If another source did, it is passive and no memory cells form.
- Add the speed and the duration.
The biological data interpretation trainer has curves of antibody levels that show the two patterns.
Check yourself
Invented case: a baby is protected in its first months by antibodies passed from its mother before birth. Name the type and give two reasons.
Answer
It is passive immunity. The baby did not make the antibodies itself, and no memory cells form, so the protection fades as the antibodies are used up.
What to study next
Turn the two patterns into graphs in reading immune-response graphs. To revisit the response itself, see explaining antigen-antibody responses.
If you want a teacher to test your comparisons, see online one-to-one Biology tuition.