Active and Passive Immunity
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of immune responses and the sources of antibodies in different contexts. You can test your knowledge on these below.
What is the role of B-lymphocytes in immunity?
B lymphocytes produce plasma cells that secrete antibodies and form memory cells for long-term immunity.
What are antigens?
Molecules, usually proteins, that trigger an immune response.
What is the difference between the primary and secondary immune response?
- The primary response is slow and occurs after the first exposure to an antigen.
- The secondary response is faster and stronger due to the presence of memory cells.
Topic Explainer Video
Check out this @LauraDoesBiology video that explains active and passive immunity or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Immunity Explained
- Immunity is the ability of an organism to resist infection by producing a specific immune response.
- Two main types:
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Active Immunity: The immune system actively produces its own antibodies.
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Passive Immunity: Antibodies are introduced from an external source.
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Active Immunity
- Occurs when the immune system produces its own antibodies in response to an antigen.
- Active immunity will lead to the production of memory cells.
- Types of Active Immunity:
- Natural Active Immunity:
- Acquired through infection by a pathogen.
- Example: Chickenpox – Once recovered, a person has lifelong immunity.
- Artificial Active Immunity:
- Acquired through vaccination containing weakened or inactive pathogens.
- Example: MMR vaccine – Stimulates the immune system to produce memory cells.
- Natural Active Immunity:
Passive Immunity
- Occurs when antibodies are introduced from an external source, such as pre-made antibodies extracted from human or animal blood, rather than being produced by the body.
- Passive immunity does not lead to the production of memory cells.
- Types of Passive Immunity:
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Natural Passive Immunity:
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Antibodies are transferred naturally from mother to baby.
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Example: Breast milk contains maternal antibodies that protect the baby from infections.
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Artificial Passive Immunity:
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Pre-made antibodies are injected to provide immediate protection.
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Example: Snake antivenom – Contains antibodies extracted from animals to neutralise venom.
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Comparison of Active Immunity & Passive Immunity
Active Immunity
| (✓) | (x) |
| Plasma cells produce antibodies. | Takes time to develop. |
| Memory cells are formed. | Risk of developing symptoms if acquired naturally. |
| Long-lasting immunity. | Some vaccines require booster doses. |
Passive Immunity
| (✓) | (x) |
| Immediate protection. | No memory cells are formed. |
| Useful for emergancy situations (e.g. antivenom). | Short-term immunity. |
| Helps protect immunocompromised individuals. | Risk of allergic reactions to injected antibodies. |
Real-World Example: Tetanus Protection
- Active Immunity:
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The tetanus vaccine contains an inactivated form of the tetanus toxin (toxoid), stimulating the immune system to produce memory cells.
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Provides long-term protection but requires boosters every 10 years.
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Passive Immunity:
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If someone has not been vaccinated and is exposed to tetanus, they receive tetanus antitoxin (TIG – Tetanus Immune Globulin).
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Provides immediate but temporary protection.
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Key Terms
- Active Immunity: When the individuals own plasma cells produce antibodies and memory cells are formed.
- Passive Immunity: When antibodies are transferred into the individual from another source.
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Exam Tip
For passive immunity, emphasise that no immune response occurs since antibodies are introduced externally and therefore immunity is not long term (there are no memory cells produced).
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Contrast active and passive immunity. (3 marks)
- Active immunity occurs when the immune system produces its own antibodies after exposure to an antigen, while passive immunity involves receiving antibodies from an external source.
- Active immunity forms memory cells, leading to long-term protection, whereas passive immunity does not produce memory cells and provides only short-term protection.
- Active immunity takes time to develop, but passive immunity provides immediate protection.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!