Bau Ur, Second Life asked:
If pregnant women gain an immune advantage from the foetus, does this explain better immunity in mothers?
Chris - The answer is no, because the same gene which is used by a baby is used by these women because they carry it anyway. They're just activating it in a different set of tissues to get the same effect as the gene would have in a baby developing inside the mother, but at a totally different site.
That's what's wonderful about the huge genetic recipe book we have. We can redeploy the genes and their functions all over the body to do the same job in different places or even by tweaking the gene a bit, a totally different job, using almost the same gene.