Types of Immunity: Active and Passive
Active immunity develops when the body makes its own antibodies after exposure to an antigen and provides long-lasting protection, while passive immunity comes from antibodies made by another organism and gives immediate but temporary protection.
One-hour paid trial · Same-day reply
Active immunity
Active immunity develops when a person's own B-lymphocytes are stimulated by an antigen and produce antibodies against it. Because the correct lymphocytes must first be identified and allowed to multiply, active immunity takes time to build up, but it leaves behind memory cells, giving long-lasting protection.
Natural active immunity develops after actually catching and recovering from a disease. Artificial active immunity is produced by vaccination, in which a weakened, inactivated or partial form of a pathogen is deliberately introduced to trigger the same immune response and memory cells, without causing the full disease.
Passive immunity
Passive immunity occurs when a person receives ready-made antibodies produced by another organism, rather than making their own. Because the antibodies are already active, protection begins immediately, but it does not last, since the body's own B-lymphocytes were never stimulated and no memory cells are formed, the borrowed antibodies simply break down over time.
Natural passive immunity happens when antibodies pass from a mother to her baby across the placenta before birth, or through colostrum in breast milk afterward. Artificial passive immunity is given by injecting antibodies produced in another person or animal, such as anti-venom after a snakebite.
Comparing the four types
| Type | Antibody source | Onset of protection | Duration |
|---|---|---|---|
| Natural active | Own body, after actual infection | Slow | Long-lasting |
| Artificial active | Own body, after vaccination | Slow | Long-lasting |
| Natural passive | Another organism (e.g. mother, via placenta or breast milk) | Immediate | Short-lived |
| Artificial passive | Another organism (e.g. antibody injection) | Immediate | Short-lived |
How it is examined
Exam questions on this standard often describe a scenario, such as a baby being breastfed, a person recovering from measles, or someone receiving a vaccine or an antibody injection, and ask you to classify it as natural or artificial, active or passive. You may also be asked to explain, using the idea of memory cells, why active immunity lasts longer than passive immunity.
Worked exam-style question
Question. A person receives a tetanus vaccine after a minor injury, and a separate person who has just been bitten by a snake receives an injection of anti-venom. (a) Classify the type of immunity given by (i) the tetanus vaccine and (ii) the anti-venom injection.
(b) Explain why the tetanus vaccine provides protection that can last for years, while the anti-venom injection only protects for a short time. (c) Name the type of white blood cell responsible for producing antibodies in active immunity.
Model answer. (a) (i) Artificial active immunity. (ii) Artificial passive immunity.
(b) The tetanus vaccine stimulates the person's own B-lymphocytes to produce antibodies against the antigen and, importantly, to form memory cells, which remain in the body and allow a fast antibody response if the same pathogen is met again; the anti-venom injection supplies ready-made antibodies from another source without stimulating the person's own lymphocytes, so no memory cells are formed and the borrowed antibodies simply break down over time. (c) B-lymphocytes.
Practice question
Try this. A newborn baby who is exclusively breastfed for the first six months rarely falls ill with the same infections that affected the mother during pregnancy, but this protection fades within the first year of life. (a) Name the type of immunity the baby receives through breast milk.
(b) State whether this immunity is natural or artificial, and explain why. (c) Explain why this protection does not last.
Exam tip
Key terms
- Immunity, the body's ability to resist infection by a particular pathogen.
- Antigen, a foreign molecule, often on a pathogen's surface, that triggers an immune response.
- Antibody, a protein made by white blood cells that binds to a specific antigen to help destroy pathogens.
- Vaccine, a preparation of weakened or inactivated antigens given to stimulate active immunity without causing the disease.
Source:SRC-DSKP-EN
Frequently asked questions
What is the difference between active and passive immunity?
Why does a vaccine provide long-lasting protection but an anti-venom injection does not?
More for Immunity in Humans
Related
One-hour paid trial · Same-day reply