Passive Immunity
Thus far, all the acquired immunity we have discussed
has been active immunity. That is, the person’s own
body develops either antibodies or activated T cells in
response to invasion of the body by a foreign antigen.
However, temporary immunity can be achieved in a
person without injecting any antigen. This is done by
infusing antibodies, activated T cells, or both obtained
from the blood of someone else or from some other
animal that has been actively immunized against the
antigen.
Antibodies last in the body of the recipient for 2 to
3 weeks, and during that time, the person is protected
against the invading disease. Activated T cells last for
a few weeks if transfused from another person but
only for a few hours to a few days if transfused
from an animal. Such transfusion of antibodies or T
lymphocytes to confer immunity is called passive
immunity.
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