Passive immunity
Exam-ready definition
Short-term defence against a pathogen by antibodies acquired from another individual, for example from mother to infant through the placenta or breast milk.
How this is marked
The two paying points are that the antibodies come from another individual (not made by the body) and that the protection is short-term. Because no memory cells are made, immunity is not long-lasting. Students lose marks by confusing it with active immunity; the key word examiners test is whose antibodies they are. Breast milk and the placenta are the standard examples.
In an exam answer
On a newborn's protection: 'A baby gains passive immunity from antibodies in its mother's breast milk, but this is short-term because the baby does not make its own antibodies or memory cells.'
Full topic guide: Diseases & immunity
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