Fetal tissue is unique since it is fast growing and has a lower possibility of rejection from the host's immune system than adult cells.
In 1982, seven people in Santa Clara County, California were diagnosed with Parkinsonism after having used MPPP contaminated with MPTP.
In 1992, two of the seven patients were successfully treated at Lund University Hospital in Sweden with neural grafts of fetal tissue.
[1] Because the source of the tissue is aborted fetuses, there are significant legal and ethical issues being discussed.
Federal funding for embryonic tissue research was restricted in the United States under Presidents Reagan and Bush before being lifted under the Clinton administration.