1. Protecting the body
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2. Barriers and defences
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3. The immune system
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4. Primary and secondary immune responses
The immune response is much faster and larger when the pathogen infects the body again, because of memory lymphocytes left in the blood after the previous infection.
The secondary response can destroy pathogens so quickly that you don’t feel ill – you have become immune to that infection.
Immunity to one pathogen doesn’t usually produce immunity to other pathogens, because their antigens are different.
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5. Immunisation means to make someone immune to a particular infection.
Immunisation can be done by giving a person a vaccine.
A vaccine contains weakened or inactive pathogens, which have the antigens but won’t make you ill.
The antigens cause a primary immune response, as if you had been infected by the live pathogen.
Memory lymphocytes are left in the blood that match the antigens.
If you are infected with live pathogens of the same type, your body will produce a secondary response, which stops you being ill.
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6. Antibiotics are medicines used to treat bacterial infections.
Antibiotics work by damaging processes that happen in bacteria but not in human cells.
Antibiotics cannot be used to treat viral infections (e.g. colds or flu) because viruses do not have cell processes.
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7. Stages in developing a new medicine
Carried out on …
Done to check …
first
(pre-clinical)
diseased cells and tissues in the lab
that the medicine gets into cells and damages the pathogen
second
animals in lab
how medicine affects a whole body without risking humans
small clinical trial
a few healthy people
that the medicine has few harmful side-effects
large clinical trial
many people who have the disease that the medicine will treat
the right dose to give, and whether different groups of people suffer different side-effects
A side-effect is an unintended effect, which may be harmful.
The dose is the amount of medicine given to the patient at one time.
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