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What type of white blood cell produces antibodies?
Lymphocytes
What do antibodies bind to on a pathogen?
Antigens
What cells engulf and digest pathogens?
Phagocytes
What is the first immune response called?
The primary immune response
What is a vaccine usually administered by?
Injection
Why might a person feel ill during their first infection?
Because it takes a few days for antibodies to be produced.
What happens to antibody levels after the infection has been cleared?
They decrease but do not fall to zero.
What type of cells remain in the blood after the first infection?
Memory cells
What is the immune response called when exposed to the same pathogen again?
The secondary immune response
What does a vaccine contain?
A dead, inactive, or part of a pathogen
Why is the secondary immune response faster?
Because memory cells respond quickly and produce antibodies rapidly.
How do antibodies help phagocytes destroy pathogens?
They cause pathogens to clump together, making them easier to engulf.
Why does a person usually not feel ill during a second infection?
Because antibodies are produced quickly and destroy the pathogen before symptoms develop.
Why must a new flu vaccine be made each year?
Because the influenza virus mutates and new strains emerge.
Why are two doses of the MMR vaccine usually needed?
To ensure a strong and long-lasting immune response.
Why does each lymphocyte produce only one specific antibody?
Because each lymphocyte has a receptor that is specific to one antigen.
Why might someone vaccinated against an original flu strain still get infected?
Because the virus may have mutated and changed its antigens.
Why don’t antibody levels fall to zero after infection?
Because memory cells remain in the blood and can produce more antibodies.
How does vaccination provide immunity without causing disease?
It exposes the immune system to a harmless form of the pathogen, triggering antibody and memory cell production.
Why are elderly people encouraged to get the flu vaccine every year?
Because they are more vulnerable (weaker immune systems) and new flu strains emerge annually.
What would happen if memory cells did not remain in the blood?
The body would not respond quickly to reinfection and the person would become ill again.
Describe the sequence of events in the primary immune response.
Pathogen enters → lymphocytes recognise antigens → antibodies are produced slowly → pathogens are destroyed → memory cells remain.
Compare the primary and secondary immune responses.
The primary response is slow and may cause symptoms; the secondary response is faster, stronger, and usually prevents illness.
Why does mutation make vaccine development difficult?
Mutations change the antigens, so existing memory cells cannot recognise the pathogen.
A vaccinated person is infected but shows no symptoms. Explain why.
Memory cells produce antibodies quickly, clearing the pathogen before symptoms develop.