This week we've been sequencing Lorianna's question: if babies have different genetic sequences from their mother, and are technically foreign objects in the womb, why doesn't the mother's immune system attack? Ziyad Yehia asked Dr Lucy Fairclough, an immunologist from Nottingham University to find out...
Often the fetus IS rejected.
This question was referring more specifically to the immune rejection of a developing foetus and what prevents this from happening, given the close contact between foetal and maternal tissues. Your point about early failure of embryos to implant is a good one though and points to a genetic selection process. chris, Sun, 14th Jun 2015
But can we be sure that the immune system is innocent in <<all>> if not most aspects of fetal wastage? If there is a genetic problem, what would suss that out but the immune system?
I've read that humans and other placental mammals make use of an endogenous virus carried in our DNA that is activated within the placenta. I had the impression that the virus had mastered the art of hiding from the immune system and our ancestors incorporated it as a tool enabling foetal growth within the body without sealing the baby in an egg.
I would guess that the ovum, by containing the lion's share of the material needed to form the fetus, by being formed by the mother is is accepted by her body. The male DNA, upon fertilization, is only a small fraction of the total mass and becomes hidden away from her immune system, which sees only the bulk mass.
Another question in a similar vein (excuse the pun): why doesn't the immune system reject blood transfusions? vhfpmr, Mon, 16th Nov 2015