The immune system 🤒
- engulf pathogens and destroy them
- produce antibodies to destroy pathogens
- produce antitoxins that neutralise the toxins released by pathogens
In I/GCSE Biology, pathogens contain certain chemicals that are foreign to the body, called antigens. White blood cells - lymphocytes - carry antibodies - proteins that have a chemical 'fit' to a certain antigen. When a white blood cell with the appropriate antibody meets the antigen, it reproduces quickly and makes many copies of the antibody that neutralises the pathogen.😜
Vaccination 💉
People can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens. Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body.
Vaccines can contain:
- live pathogens treated to make them harmless
- harmless fragments of the pathogen
- toxins produced by pathogens
- dead pathogens
In I/GCSE Biology, these all act as antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen. 😷😷
Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease - although some people may suffer a mild reaction. If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it.
Advantages of vaccination 👍
- safe to use and can be given to immuno-deficient and pregnancy individuals
- cheaper than live attenuated vaccine
- storage not as critical as live vaccine
Disadvantages of vaccination 👎
- microorganisms cannot multiply so periodic booster must be given to maintain immunity
- only humoral immunity can be induced
- most killed vaccines have to be injected
- some vaccines such as Mordetella pertussis induce side effects like post-vaccinial encephalomyelitis
- inactivation such as formaldehyde in the case of Salk vaccine, may alter antigenicity
That's the end of the topic!
Drafted by Joey (Biology)