A year ago, when chemotherapy stopped working against his leukemia and he had nothing to lose, William Ludwig signed up to be the first patient treated in a bold experiment at the University of Pennsylvania.

Doctors removed a billion of his T-cells — a type of white blood cell that fights viruses and tumors — and re-engineered them to attack his cancer. Then the altered cells were dripped back into Mr. Ludwig's veins.

At first, his vital signs took a nose-dive and doctors thought he might die.

But, a few weeks later, "the fevers were gone. And so was the leukemia."

(READ the amazing story in the New York Times) – Photo from University of Pennsylvania