I don't often post to Lactnet, but felt that as an immunologist I could contribute something to this
particular discussion.
This is in regard to paper that Ellen brought to our attention (American Journal of Pathology.
2006;168:608-620) The premise of the study was that inflammatory mediators make a tissue
more prone to tumor cell metastases and the evidence suggests that this is true. However,
inflammation is not a part of normal breast involution (see below).
The experiments in this particular study were based on the results of two previous studies:
Clarkson RW, Wayland MT, Lee J, Freeman T, Watson CJ: Gene expression profiling of mammary
gland development reveals putative roles for death receptors and immune mediators in post-
lactational regression. Breast Cancer Res 2004, 6:R92-R109[
Stein T, Morris JS, Davies CR, Weber-Hall SJ, Duffy MA, Heath VJ, Bell AK, Ferrier RK, Sandilands GP,
Gusterson BA: Involution of the mouse mammary gland is associated with an immune cascade and
an acute-phase response, involving LBP, CD14 and STAT3. Breast Cancer Res 2004, 6:R75-R91
In these two previous studies the authors performed gene chip analysis comparing RNA from
mammary gland tissue from either pregnant mice, lactating mice, and mice with mammary glands
undergoing involution. They found that the involuting mammary glands had high expression of
inflammatory markers -- it is important to note that these inflammatory markers were NOT seen
in either the glands from the pregnant or lactating mice.
In all of three studies, the mice and rats were weaned abruptly and this is the key point. Pups were
removed from the mother at day 1, 2,3,4 and 20. Mice normally wean on their own by day 21 and
it was interesting that the inflammatory markers were NOT seen at day 20 in glands that were
involuting normally.
Abrupt weaning at those early times (day1,2,3 &4) is not the biologically normal way to wean. We
know that weaning should be gradual to avoid plugged ducts and mastitis which are indeed
inflammatory processes.
This is a good example to show how lactational physiology is misunderstood by the medical and
scientific communities. And it highlights how important breastfeeding support is, women with
good information and support will be less likely to have plugged ducts and mastitis, and so will
not have inflammation in the breasts.
Laurie Shornick, Ph.D.
St. Louis, MO
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