Dear Marcia,

Here is a quick summary of the immunobiology of antibodies,  
autoimmune disease, pregnancy & lactation.

Our bodies make several types of antibodies. For this discussion the  
two main types are IgG and IgA.

IgG is transferred during pregnancy from the mother's circulation  
into the babies circulation. There is an accumulation of antibodies  
over the course of the pregnancy. Thus, a baby born prematurely would  
not yet have received all the antibodies that a term baby would  
receive. These IgG antibodies will remain in an infant's circulation  
for around six months and then they disappear. In the meantime, the  
infant has not yet developed the full capacity to make it's own  
antibodies yet. This is just one reason why it is so important for  
the infant to receive antibodies from breastmilk (and I will explain  
why these antibodies are special further on).

IgG antibodies are great for getting rid of bacteria and viruses in  
the blood or tissues. When IgG binds to a bacteria this activates a  
collection of proteins known as complement. These proteins coat the  
surface of the bacteria or virus and poke holes in it so that it will  
die. Very effective system, although it also induces  inflammation.

However, if a person has an autoimmune disease they will make  
antibodies against their own proteins. In this case, the mother's  
body makes IgG antibodies against her own neutrophils. The anti- 
neutrophil IgG binds to the surface of her neutrophils, complement  
gets activated, and pokes holes in the cells causing them to die.  
This explains why she has fewer neutrophils.

Neutrophils are the "first responders" of all our immune cells and  
they are especially good at killing bacteria. Someone who is  
neutropenic may have trouble clearing bacterial infections.

Now as I mentioned, the IgG from the mother is transferred to the  
fetus during pregnancy. This would include the anti-neutrophil IgG  
antibodies that the mother is producing. So, her baby is receiving  
these antibodies in utero. This is not a problem because the baby is  
also protected from infection in the womb. However, after the baby is  
born it will still have these antibodies in it's system for about six  
months which could cause the baby to be neutropenic for awhile as  
well. This also happens with neonatal lupus: the maternal autoimmune  
antibodies are passed to the baby during gestation and the newborn  
will have lupus symptoms for about six months until those antibodies  
wear out.

Now here's the great news. The main antibody in breastmilk is IgA and  
it works in a different way than the IgG type. This IgA type of  
antibody is produced on all our mucosal surfaces (the lining of the  
respiratory tract & the lining of the gastrointestinal tract) which  
are the main places where we encounter bacteria and viruses. The  
first thing that the bacteria or virus needs to do to infect us is to  
bind to the lining of our respiratory or GI tract, BUT the IgA type  
of antibody binds to the bacteria or virus and actually BLOCKS it  
from binding to us at all. In other words, it can prevent infection  
from even being established. Or reduce it to the level where there  
aren't any symptoms. This mechanism also does not cause any  
inflammation.

So, after this baby is born it may be slightly neutropenic and  
therefore more susceptible to infection. However, if the mother is  
breastfeeding, the IgA antibodies in the milk will work to prevent   
infections from being established in the first place. Therefore, the  
baby may have fewer neutrophils for awhile, but that shouldn't matter  
because it will be well protected by the IgA antibodies that it will  
receive through the breastmilk. Also, the IgA antibodies are designed  
to travel through the digestive tract without being degraded.

I hope that this information is helpful. Feel free to contact me  
offlist if you have additional questions.
Warm regards,
Laurie Shornick, PhD

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