Immunisation

Immunisation

The first time that you are exposed to an antigen, it takes over a

week for plasma cells to produce sufficient antibodies to inactivate

the antigen (primary response).

On second exposure, when

helper T cells present the

antigen to memory B cells,

the memory B cells quickly

produce plasma cells which

make large amounts of

antibody (secondary

response). This inactivates

the antigen before you get

sick.







This is active immunity- the body actively producing antibodies.



Sometimes subjects are given large amounts of antibodies from

another source, which inactivate the antigen (passive immunity).

For example, breast milk contains large amounts of antibodies

produced by the mother. This provides some protection for the

infant while their own immune system develops.



Sometimes antibodies are needed very quickly- during the time

that it would take for the patient to produce them they would die.

They can be given antisera (singular= antiserum), antibodies

produced from the blood of animals like horses. E.g. following snake

bite, patients are given antiserum which contains antibodies against

the snake venom.



Natural immunity is when the body produces antibodies against a

pathogen due to previous natural exposure.

Artificial immunity is when protection is due to immunisation.



Immunisation- the subject is exposed to an attenuated (weakened)

or killed version of the bacteria or virus.

 The body produces antibodies & memory cells (primary

response)

 If exposed to the pathogen later, memory cells detect the

antigen & antibody production occurs very rapidly (secondary

response)



Questions

1. A child catches chicken pox at the age of six. He is later

exposed to chicken pox but doesn’t get sick. Is this active or

passive immunity?

2. Antibodies pass from the placenta to an infant just before

birth. Is this active or passive immunity?

3. If the antibodies in antisera are proteins from horses or

cows, what is a possible risk of administering them to

humans?



 Benefits

 Some diseases can be completely eradicated e.g.

smallpox

 Death & long term disabilities caused by disease are

decreased e.g. prevention of disabilities caused by

prenatal rubella

 Financial benefits due to less time lost due to illness

 Herd immunity- if >90% of the population are immune

disease can’t spread between people

 Dangers

 Immunity may only last for several years, requiring

booster shots

 Herd immunity may cause complacence, less

immunisation & the disease can re-emerge

 Some vaccines may cause side effects

 If attenuated live vaccines are used, the possibility

exists for the organisms to mutate & cause disease

again