what is the different between passive and active immunity?

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  • iuh8ui
    Lv 4
    10 years ago
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    Active immunity is where the immune system is exposed to a non-self antigen (any molecule that sets off an immune reaction) and the sensitised immune system makes infection fighting cells (B and T lymphocytes) to destroy the invading pathogen.

    Passive immunity is where protection from disease is provided by antibodies (infection fighting proteins made by B lymphocytes) from another person/animal - ie the immune system of the person receiving the protection from disease does not fight off the infection.

    Active immunity can be natural (occurs without human intervention) when a person catches a disease. Or it can be artificial (occurs with human intervention) in the case of vaccination.

    Passive immunity is natural when antibodies from a mother cross the placenta to the fetus or when the infant receives maternal antibodies in the breastmilk. It is artificial when antibodies made in and collected from another person/animal (usually horses) are given as an injection.

    Active immunity is long lasting (sometimes lifelong) as the memory cells produced after the exposure can last for years. Passive immunity lasts only as long as the antibodies remain in circulation - about 6 months.

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