One of the most remarkable aspects of reproductive
biology is the simple fact that a healthy
woman with a fully functional immune system
can successfully carry a semiallogeneic pregnancy
to full term without immune rejection. A recent
study by Samstein and colleagues1 provides new
insights into the mechanism of maternal–fetal
tolerance and suggests that our previous notions
have been naive. This study may also explain
why prior approaches to preventing immune rejection
of the fetus by the mother have failed and
suggests an alternative approach to treatment