Vaccination Creates Memory Without Disease
Vaccine
A substance containing dead or inactive forms of a pathogen, or its antigens, that is given to make a person immune to a disease.
- A vaccine contains an inactive or harmless form of a pathogen, or antigens from it.
- The vaccine antigens cannot cause the full disease but are recognised as foreign.
- An inactive pathogen retains antigens that lymphocytes can recognise but cannot reproduce and cause the full disease.
Immunisation produces a primary immune response before exposure to the active pathogen.
Lymphocytes Produce Antibodies and Memory Cells
Vaccination
Introducing a harmless form of a pathogen into the body so the immune system produces antibodies and memory cells, giving protection against future infection.
- Lymphocytes with complementary receptors are activated and divide.
- Some cells produce specific antibodies, while others remain as memory cells.
Later Exposure Triggers a Rapid Response
Memory cell
A white blood cell that stays in the body after an infection so the body can respond faster and more strongly if the same pathogen returns.
- Memory cells recognise the same antigen when the live pathogen enters later.
- They divide rapidly and produce a larger concentration of antibodies in less time.
- The pathogen is destroyed before it causes serious symptoms.
- On later exposure, memory cells recognise the same antigen and produce antibodies before pathogen numbers become high enough to cause symptoms.
After vaccination, measles antigens activate memory cells, so later exposure produces antibodies quickly enough to prevent measles developing.
Booster Doses Restore Protection
- Memory-cell numbers or antibody concentrations can decline over time.
- A booster exposes the immune system to the antigen again and strengthens the memory response.
- A booster repeats antigen exposure, increasing memory-cell numbers and restoring protection when immunity has declined.
A vaccine does not act by killing pathogens directly because it trains the immune system to respond.
Write the Full Immunisation Chain
- Clonal selection and mitosis produce antibody-secreting cells and memory lymphocytes during the primary response.
- Use the order: inactive pathogen or antigen, lymphocyte activation, antibody production, memory-cell formation, faster secondary response.
- Include specificity by stating that antibodies bind the same antigen.
Immunity Is Produced Actively
Active immunity
Long-lasting protection that comes from the body making its own antibodies after meeting a pathogen, through infection or vaccination.
- Vaccination gives active immunity because the person's own lymphocytes produce antibodies and memory cells.
- This protection can last much longer than receiving ready-made antibodies.
- What does a vaccine contain?
- Why does it not cause the full disease?
- How do memory cells protect after vaccination?
- Why might a booster be needed?
