Because the placenta protects the fetus from the maternal immune system, its tissue is considered immunologically privileged: Even though it’s technically foreign tissue, placental grafts have been found not to prompt an immune response in transplant recipients. That means, unlike skin grafts from animals or cadavers, placental grafts are basically not rejectable. The placenta’s tissue also contains proteins and sugars that spur patients’ cells to multiply quickly, and the grafts have been shown to encourage rapid skin and tissue regrowth. In one case, doctors essentially regrew the tip of someone’s nose.1