11.   One earlier attempt at the procedure has failed, but animal experiments suggest that this time, the transplant might work, thanks to a new discovery in immunology.

12.   Standard cornea transplants had not worked because the people did not have cells needed to grow a new protective covering over the cornea.

13.   The islet transplants worked in small animals, so the researchers tested monkeys, traditionally the last step before a human trial.

14.   The researchers said it is unclear how the transplants might work, but the they aim to replace lost nerve cells.

15.   Thus, if the transplants ultimately work, there would be a shortage.

16.   Within two to four weeks, doctors will have an initial indication of whether the transplant is working, Yeager said.