passive immunity
(PA-siv ih-MYOO-nih-tee)
A type of immunity that occurs when a person is given antibodies rather than making them through his or her own immune system. For example, passive immunity occurs when a baby receives a mother's antibodies through the placenta or breast milk. It can also occur when a person receives an injection of antibodies to protect against the effects of a toxin such as snake venom. Passive immunity provides immediate protection but only lasts a few weeks or months.