Final answer:
Passive immunity is acquired when antibodies from another person or animal are transferred to an individual, providing immediate but temporary protection against a pathogen.
Step-by-step explanation:
You develop passive immunity when you receive antibodies from another person or an animal. Passive immunity is a form of short-term immunity to a particular pathogen that results when antibodies or activated T cells are transferred to a person who has never been exposed to the pathogen. This can happen naturally, such as antibodies passed from mother to child during pregnancy or through breast milk, or it can be done artificially, like receiving an injection of antibodies for snake venom or other medical treatments.
Passive immunity transfer of antibodies provides immediate protection because the body doesn't need to take the time to create its own response to the pathogen. However, this sort of immunity is temporary, as the transferred antibodies will eventually degrade and not provide long-term protection like active immunity does through the production of memory lymphocytes in response to a pathogen.