An interesting article and one wonders what nature can do ?
Of all the miracles of life, here’s by far the most miraculous of all: Women’s bodies, for the most part, do not attack and destroy the fetus growing inside them.
From an immunologic point of view, the fetus is an alien. Like a germ. Or an organ transplant. And your body is programmed to mount an assault on foreigners. But my fetus is half me, you say. And so, you may suspect—as others have before you—that the “half-me” part signals the body to avoid all-out warfare. This makes emotional sense! But the success of surrogate moms and donor eggs—with women gestating babies produced by the eggs of other women, their bodies accepting the presence of a fetus that is not “half-them”—proves that idea wrong.
So that leads us to the big question: Why does pregnancy even work?
Pregnancy, as Yale School of Medicine’s Harvey Kliman sees it, is a metaphor for marriage. The placenta is controlled by the father’s genes, the embryo by the mother’s. Each side has its own agenda. Yet, the key to a successful union—whether it be mother and fetus, or husband and wife—is compromise. The details of this compromise have always been a mystery, but in the past few years, scientists seem to be edging closer to understanding the specific negotiations that occur deep within the cells of the women’s body that allow the fetus to escape destruction.
For years, doctors have been eyeing T cells, the immune cells that attack and destroy invaders (which should include the fetus). A few years ago, a team of researchers at NYU School of Medicine, lead by Adrian Erlebacher in the department of pathology, discovered something that had never been seen before: In pregnant mice, even when the T cells were experimentally nudged into attack mode, they did not bite.
These early studies prompted the NYU team to dig deeper, trying to figure out the chain of events that would stop the T-cell attack. They eyed a certain family of genes that, when working properly, recruit and send T cells marching toward invaders. But in the pregnant mouse, the genes were silenced in the decidua—the tissue surrounding the fetus and the placenta—by a chemical that attached to the genes’ proteins, altering the way the genes look and therefore how they act. With this physical change, the genes can no longer communicate “attack!” to the T cells.
The upshot: In a pregnant mouse, at least, the genes can’t do their job, which means that the cascade of events that would lead to an immune assault on the fetus never happens.