We all know that mothers perform amazing feats every day. But did you know that biologically, the act of becoming a mother actually defies nature?
That’s right. The process of successfully carrying a child to term, from a purely immunologic standpoint, should not happen. By rights, a woman’s body should see the fetus as a foreign body, an invader – and reject it.
And yet, most of the time, it doesn’t. Some have argued that this is because the fetus contains half the mother’s genes, so the body’s normal immunologic response is somehow calmed. But that doesn’t explain how surrogate moms – women with no genetic connection to their fetuses – can have successful pregnancies.
So, why does pregnancy work? Recent findings by Sing Sing Way, MD, PhD, a physician researcher in the Division of Infectious Diseases, shed new light – and may help explain why first pregnancies have a higher risk of miscarriage or premature delivery. Way’s discovery might well lead to a vaccine that would help prevent preterm birth.
Quieting the immune response
For some time, in trying to understand why pregnancy is exempt from the normal immune response, scientists have focused on T cells. These are the immune system’s defense mechanism, cells that attack and destroy things that invade our bodies. During pregnancy, a woman’s immune system suppresses the T cells so that they do not attack the fetus.
Way’s study took this idea further, showing that these suppressed T cells – called CD4 cells – remain in a woman’s body after pregnancy, and re-activate in subsequent pregnancies. This ensures that future pregnancies are protected even more against rejection.
Way’s findings, published recently online in the journal Nature, explain why the chance of miscarriage and other complications drops in second and third pregnancies.
A treatment for miscarriage?
His discovery could lead to a vaccine that would help stifle the immune response even more, something that would be helpful not only during pregnancy but also in combating autoimmune disorders such as arthritis. Stifling the immune response is precisely the opposite goal of most vaccines, which are designed to fire up the immune response to fight off viruses such as polio, measles or chicken pox.