UCSF

UCSF researchers have shown for the first time that the human fetal immune system arises from an entirely different source than the adult immune system, and is more likely to tolerate than fight foreign substances in its environment.

The finding could lead to a better understanding of how newborns respond to both infections and vaccines, and may explain such conundrums as why many infants of HIV-positive mothers are not infected with the disease before birth, the researchers said.

It also could help scientists better understand how childhood allergies develop, as well as how to manage adult organ transplants, the researchers said.