ImmunisationSpec 5.14
Immunisation gives protection from a disease without having to catch it. A person is given an inactive form of the pathogen, for example a dead or weakened one, usually by injection.
- The inactive pathogen is put into the body. It cannot cause the disease, but its antigens are still present.
- The antigens trigger an immune response and antibodies are made.
- Memory lymphocytes are produced.
- If the live pathogen enters later, the memory lymphocytes carry out a fast secondary response. Large numbers of antibodies are made quickly and the person does not become ill.
| Natural infection | After immunisation | |
|---|---|---|
| Pathogen present | Live pathogen | Inactive pathogen, which cannot cause the disease |
| Memory lymphocytes made? | Yes | Yes |
| Person becomes ill? | Yes, during the first (primary) response | No |
Doctors sometimes give a second injection, called a booster, to increase the number of memory lymphocytes made.
Quick check
Name two physical barriers in the human body.
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Any two of: skin, mucus, cilia.
What do lysozymes do?
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They are enzymes that break down the cell walls of bacteria.
What is an antigen?
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A molecule, usually on the surface of a pathogen, that triggers an immune response.
Why is the secondary response better than the primary response?
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Memory lymphocytes make it faster and produce more antibodies.
Triple only: what is herd immunity?
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When a large proportion of the population is immune, so the pathogen cannot spread easily and non-immune people are protected.