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5.3 outline the way in which vaccinations prevent infection
outline the way in which vaccinations prevent infection
Background
When a person has had an infection, some of the B cells produced in response to the pathogen are stored in the lymphatic tissue. They are called memory B cells. They are ready to provide a very rapid response if the same pathogen later attacks the body.
- Vaccination is a way of giving a person the “experience” of having had an infection without actually having it, so that the body responds to the “experience” by producing the appropriate memory B cells.
- The way in which the “experience” is given depends on the pathogen. In the case of small pox a very similar, but very much less harmful pathogen (cow pox), was used. In other cases, the virus is made weaker, and therefore harmless (attenuated), before being used in a vaccine. Examples of this type of vaccine are those for poliomyelitis, measles and whooping cough.
- Many pathogenic bacteria are harmful to the body because of the toxins they produce. For diphtheria these toxins are modified to produce the vaccine.
- Whatever the source of the vaccine, the effect is the same. It introduces antigens into the body so that B cells are activated to produce large amounts of antibody and B cells that are stored in the lymph system are ready for a future attack by the particular pathogen.