Why Doesn't the Mother's Immune System Reject the Fetus?

One of the most interesting and long-standing questions in immunology is why the fetus, an allogeneic graft, is not rejected by the mother's immune system. Is there some anatomic barrier between mother and fetus that prevents it? Is the fetus antigenically "immature", not yet able to produce antigens that attract the attention of the maternal immune system? Past research says no.

A third hypothesis suggests that the mother is incapable of mounting an immune response against the fetus. But why? A team from the Medical College of Georgia may have found the answer, at least in mice, in an elegantly simple set of experiments. They demonstrate that, in fact, maternal T cells recognize the fetus as foreign and mount an attack: the fetus then activ…