The human immune system is not short of fantastic. If you were to think of it as an army, it’s an army that can take heavy losses but keeps on going. It’s an army that has an almost limitless amount of raw material to act against invaders. It’s an army that can follow a “scorched earth” policy if it needs to. It’s an army that learns its lessons. It’s phenomenal, and I am never disappointed when reading about some new finding about the immune system.
Like any other army, our immune system needs time to mature after we’re born before it can successfully take on all invaders. Lucky for us, we have some help in the way of antibodies. These little proteins can be specific and attack only a certain type of pathogen (virus, bacteria, fungus, etc.). They can also be non-specific and attack anything that is not our own.
Antibodies are created by white blood cells called “B lymphocytes”. When pieces of a pathogen are “presented” to the B lymphocytes, they create antibodies that match the antigens (proteins or sugars) on the pathogen. The antibodies will then attach to those antigens and either immobilize the pathogens – making them useless – or “tag” the pathogens for destruction. Once tagged, the pathogen is consumed by another type of white blood cell. Again, it’s a pretty phenomenal thing to imagine.
The easy acronym to remember the five types of antibodies is “GAMED”. Each antibody type is also known as an “immunoglobulin” or “Ig”. IgG is the most common one in the body, followed by IgA, then IgM, then IgE, then IgD… Hence the “GAMED” acronym. Here’s the thing, though: IgM appears first in the body after an infection, followed by IgG and the others. IgA and IgE are more present in body secretions like tears and saliva. While IgD is more found in tissues or attached to other cells (as are some IgE).
The other thing you need to remember before we dive into the meat of this post is that IgG is the only antibody that crosses the placental barrier between mother and unborn fetus. IgM is too big to cross, and the others are only found on secretions or in cells that do not cross. Finally, remember that IgG is specific. That is, you MUST be exposed to the pathogen (or its antigens, when you get a vaccine) in order to have the IgG antibodies in your blood.
Now, onto the meat.
When a women gets pregnant, her immune system is toned down. It’s not shut down, of course. That would be an evolutionary disadvantage of the highest kind. It is toned down because the fetus developing in her womb is different than her. The fetus has half of its own cells (and antigens) from the father. Unless the mother and father were closely related (a whole other post), the mother’s immune system will really not like the child if it were to encounter it. So the mother’s immune system is told to chill, AND the placenta forms a barrier to keep the mother’s white blood cells and non-specific antibodies from coming over and attacking the child.
Once born, the child has mother’s IgG antibodies for about six months, maybe a little longer. The child also has their own white blood cells, many of them. If faced with a pathogen, the child’s immune system WILL defend the child vigorously. This is why a newborn can and will have a fever from an infection. This is why a newborn can fend off the millions or billions of antigens that land on it within minutes of being born. (Think of all the hugging and kissing done those first few days after delivery. And think of where the child came through if delivered vaginally.)
Check that, don’t think about it much.
Now that you are armed with this knowledge, you can begin to understand why it is necessary for a mother to be up to date on all her immunizations. Her IgG antibodies created through exposure to diseases or through immunization will be passed on to the child and HELP protect the child for about six months after delivery. Mom’s IgA and IgE in breastmilk will also help protect the child’s airway and stomach in specific and non-specific ways. That’s why, when faced with the choice between breastmilk and formula, breastmilk is the way to go.
One more thing before we’re done here. Another thing that crosses the placental barrier is a virus. One particularly nasty virus that does this is Rubella, the virus that causes German measles. Rubella in a pregnant woman means a lot of trouble for the developing fetus. Many times, it means death. Congenital Rubella Syndrome – the name for the infection of the fetus – is horrible. You don’t wish it on your worst enemy. It causes deformities, mental retardation, blindness, and skin rashes subject to infection on the child.
There was a time when Congenital Rubella Syndrome was common in the United States. Mothers who became pregnant had to be watched carefully if they came into contact with a person who had German measles. Others were given medications and even serum from people who already had German measles in an attempt to stop the infection from reaching the fetus. Those were some dark days.
Then the vaccine (MMR in the US) came along and all that faded away into the back of our minds. Babies born with CRS are very rare in the United States, and they are usually born from mothers who were exposed to Rubella in another country. Unfortunately, this rarity also means that the anti-vax brigades say things like “Why vaccinate if it’s not around anymore?” They’re asking the wrong question, of course.
The question they should be asking is, “Why is Rubella not around anymore?” But that means that they’ll have to admit that it’s because of vaccines, and that is not happening any time soon.