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Physiology & Medicine / Why doesn't the immune system attack a pregnant woman's baby?
« on: 29/08/2008 15:05:44 »
There are a number of reasons why a baby is not attacked by the mother's immune system. Cells of the mother's immune system cannot cross the placenta into the baby. Only IgG anibodies can cross the placenta into the babies circulation, all other antibody classes are too big. The IgG which does cross the placenta is what gives the baby immunity during its first six months before its own immune system activates. Sometimes these IgG antibodies from the mother do attack the father's antigens in the baby's tissues. This is most commonly seen where a mother's antibodies attack a baby's red cells. This can and does cause intra-uterine death (called Bart's Hydrops). The reason this does not happen more often is that many of the antigens in the baby's tissues are not fully developed and the mother's antibodies do not readily bind to them.
David
Sydney, Australia
David
Sydney, Australia