For the most part, breast milk only provides antibodies until the baby's own immune system fully develops. The mother's antibodies don't stay with the baby, and the baby has to keep taking breast milk to get fresh antibodies. On the other hand, the mother is probably being exposed to the same germs as the baby, so her body is producing "tailor made" antibodies to fit the local environment. And breast milk also provides vital enzymes and other proteins which help the baby's immune system--along with all of her other organs--develop as strong as possible. We still don't know everything that's in mother's milk, but as our understanding of the roles of certain proteins develops, we keep finding more things that are in mother's milk which aren't in baby formula.

And don't overlook the other benefits as well, such as the emotional health of the baby. Breastfeeding provides a close, secure, and stable bond between the mother and baby which starts the baby on a good foundation for later life. Fifty years ago, women were told to put the baby away as soon as possible, keep them in a separate room at night, etc., which supposedly avoids spoiling the child. But we now know that it's impossible to spoil a *baby* (unlike a toddler or child). We also know that a baby who feels secure is less fussy and more free to explore their world. I'm told that one nervous young mother once went to a big, national conference of nursing mothers (La Leche League) expecting to hear a thousand screaming infants in the room. But instead all the babies were pleasantly quiet--including me.

Not sure - although thinking about it genetically, I doubt that being breast-fed by multiple women would help that much. The antibodies supplied by the woman will help the infant's immune system, but in order to continue to be useful as the infant grows, the infant must make more of these antibodies, which it can only do if it has inherited the genes to do so from its mother. I suppose that having these antibodies appear can stimulate the immune system to produce antibodies that it can, but not those that it did not inherit.

Breast milk only provides active antibodies to babies while they're nursing. Antibodies wouldn't stay for life. They're proteins, and proteins break down after a little while - days or weeks, maybe.

The baby is constantly developing its own immune system. We are, too.When my husband got hepatitis, the doctor gave me a big shot of antibodies against hepatitis, and my hepatitis was much milder than his.My body was also making its own antibodies against hepatitis. We make antibodies against things our body thinks are foreign and need to be destroyed.

These are great questions and I'm going to answer them together. You're right that infants get antibodies from their mothers. Mothers and their children are genetically different, so it is important to keep their immune systems from "fighting" during pregnancy. So the fetus does not have an active immune system until some time after it is born. The mother's immune system is also turned down, but we still don't know the detail of how she fights off infections without her body attacking her unborn child.

Since the infant will need to start fighting off infections as soon as it's born, it gets antibodies from its mother. This is called "passive immunity." However, these antibodies have the mother's "ID tags," on them, so as the baby's immune system starts working, it attacks them. This works out fine, because the antibodies are there when they're needed most, but after a few months, when the baby's immune system is working, they are destroyed. As a result, antibodies from the mother are not passed to her grandchildren through her daughter. They are long gone while her child is still a baby. So a child who was not breasting fed will not have fewer antibodies to pass on than a child who was.

In most mammals where this has been studied, babies get their antibodies from the special milk that mothers make right around birth. This special milk is called colostrums. It is full of antibodies and other important chemicals. Colostrums are more important in some mammals than others.

As you probably know, the placenta is the thing that acts as a life support system for the embryo or fetus before it is born. Oxygen and nutrients are delivered from the mother and waste products are passed to the mother for disposal. The blood of the mother and child don't really mix, they just come very close.

In cows and horses, antibodies can't cross the placenta. Calves and foals are much more likely to get sick if they do not get colostrums. Farmers keep frozen colostrums around for baby animals that can't get it from their mothers at birth. In humans and rats, antibodies actually cross the placenta from mother to fetus before birth. So in humans colostrums are less vital, but it is probably important.

If a child feeds from several women during the first month or two of life, it may get a bigger variety of antibodies, especially if the women it was nursing from were still producing colostrums and not regular breast milk.

A veterinarian will not give a puppy a vaccination while it still has passive immunity. Can you explain why?