Oops, I see I posted this "on" lactnet despite my intent to take it off. Joy
has responded both privately and to Lactnet, and so I'm forwarding my reply
in case anybody else is also obsessing about IgM and WNV the way I am. ;-)
-- Jodine Chase
------ Forwarded Message
> From: Joy Anderson <[log in to unmask]>
>
>
>> Breastfeeding: Unraveling the Mysteries of Mother's Milk
>> from Medscape Women's Health eJournal[TM]
>> <snip>
>> Secretory immunoglobulin A (sIgA), dimeric IgA coupled to the
>> secretory component, is the main immunoglobulin in human milk. IgG
>> and IgM are also present in milk, but at much lower concentrations.
>> The changing concentration of these immunoglobulins in milk provides
>> an example of the interaction between milk components and the
>> functional development of the infant: while IgG and IgM rise rapidly
>> after birth, the newborn maintains low levels of endogenous IgA
>> during the first year of life. IgA is produced in the mammary gland
>> in B cells, which originate at maternal sites of high environmental
>> pathogen exposure (eg, the small intestine or respiratory tract),
>> and therefore protects the infant against pathogens present in the
>> immediate environment.
Thanks, Joy. I read this on Medscape as well. I had trouble parsing the
sentence: "...example of the interaction between milk components and the
functional development of the infant: while IgG and IgM rise rapidly after
birth..." I had to look elsewhere to confirm that it meant IgG and IgM rise
rapidly in the *infant* and not in breastmilk.
>
> From this it may be assumed that IgM appearing in any significant
> quantity in the baby's serum would be of infant origin, not from milk
> - yes?
Can we assume that? I don't know. I guess the issue is significant quantity.
Did the tests find a significant IgM response to WNV? In other words, lots
of antibodies?
>
> You mention 'Secretory IgM'. Please can you give me refs for this? I
> am not familiar with this type at all, but admit that my immunology
> knowledge is many years old.
I've seen several references to this, although I didn't think that the
secretory aspect of the immunoglobulin meant that it was or wasn't present
in breastmilk, so I didn't pay a lot of attention to the references. I
thought secretory referred generally to immunoglobulin that is generated in
bodily secretions - ie, mucous, saliva, etc. So if there is SIgM, it could
be SIgM produced by the baby, no?
I have also, btw, also come across the reference to *secretory* IgM
replacing the function of SIgA in people who are IgA deficient. I can't find
that reference now, though. :-/
Anyway, if you follow this link you'll get the results of a google search on
"secretory IgM" and "breast milk"
http://www.google.ca/search?hl=en&ie=ISO-8859-1&q=%22secretory+igM%22+%22bre
ast+milk%22+&meta=
----
Clearly the CDC is sure that the infant was producing its own immune
response to WNV, indicating the presence of WNV in the infant itself.
But stating this as fact without some clear info on *why* isn't helpful,
imho. We've spent the last 20 years stressing the immune properties of
breastmilk, and so it's natural, I think, for a lay person (or an IBCLC, or
a family doctor, or even a pediatrician) to wonder if the antibodies found
were from the mother via breastmilk - passively acquired, or from the baby's
own immune system generating a response to an infection.
Anyway, thanks again for taking the time to respond, Joy. I really
appreciate it.
-- Jodine
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