Fio wrote:

> We had been told by our local IBCLC that the mature
> milk antibody levels are lower than colostrum levels per unit measure,
> but that as a child ages and weans gradually, the child gets the same
> number of antibodies at, say, 2 years (while perhaps only nursing 3
> times a day or whatever) that s/he got as a 2 week old baby.  I've heard
> this before, so don't really doubt it, but we were wondering what is the
> deciding factor in the amount of antibodies that gets put into the
> mature milk?
> Does anyone know for sure how the antibody levels go up and down, or do we
>just know certain parts to the equation right now?

The common view is that the changes in concentration of defence factors such
as IgA, lactoferrin and total cells is directly related to a dilutional
effect. ie:  the greater the volume the lower the concentration, so at times
such as involution or during pregnancy, and the first few days after birth,
the concentrations are highest.

I always find it interesting that people generally think of these things in
relation to their importance to the infant. However, I lean towards the
belief that after birth the high concentrations are directed at protecting
the infant, but during involution the high concentrations are directed at
protecting the breast (as by this time if weaning is occurring at the
"natural" time (ie years), the infant's immune system is becoming pretty
well established).

However in relation to the breast, weaning reduces the flow of milk and
therefore the natural protective flushing action afforded by larger volumes
of milk (and susceptibility to mastitis is greater), therefore the
requirement for protective factors is now greater for the mother.

Having said this there is also a belief that biological factors influence
concentration, such as prematurity for instance, where the concentrations
have been found to be significantly higher than in full term colostrum.
I am continually astounded by the level of knowledge available in this area,
however there is still yet a great deal more for us to research, and the
answer(s) are likely to be a lot more complicated than I have given and
probably dependent on the interaction of many different factors.

Regards
Cathy Fetherston
Perth Western Australia

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