Library · Physiology
Passive Immunity
Make it clearer
There are two ways to be protected against an infection. One is to make your own antibodies, the defense proteins that recognize a particular invader: that is active immunity. The other is to receive them ready-made, and that is called passive immunity. They are borrowed defenses, not homemade ones.
One of those routes happens before birth: IgG is the only antibody that crosses the placenta, so the baby is born protected by the mother's antibodies, whose levels drop sharply around six months of age.
Another antibody, IgA, defends the mucous membranes, the moist linings of the gut and the airways, and it travels in tears, in saliva and in breast milk.
And passive immunity is also used deliberately. It helps people who cannot make antibodies on their own, and it is used when a disease could advance faster than the body could mount its own response.
In brief
Passive immunity means receiving ready-made antibodies rather than making your own, as in active immunity.
Borrowed defenses, not homemade: they arrive ready and get used up.
IgG is the only antibody that crosses the placenta and protects the baby until maternal levels drop sharply at six months of age.
IgA defends the mucous membranes and travels in tears, saliva and breast milk.
Passive immunity helps people who cannot make antibodies and is used when a disease could outpace active immunity.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Antibody, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingImmunization, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated