We all have an internal worry about tampering with the genes. Still, with a tiny infant's life at stake, Kohn was prepared to step across the threshold and try out this potentially lifesaving therapy. Andrew gets an injection of ADA enzyme. The approach he developed was to collect the 100 mL of blood left behind in Andrew's umbilical cord and placenta, which is normally thrown away. This blood, called cord blood, is rich in blood-forming stem cells, identical to those found in bone marrow.
Stem cells give rise to a host of blood cells.
In fact, cord blood is now being used as a substitute for bone marrow in restoring immune systems. The problem with using Andrew's cord blood was that the cells lacked a functioning ADA gene and were no better than the immune cells he already had. So, Kohn's next task was to insert DNA containing a working ADA gene into these cells. This was no small task. Because DNA will not simply enter cells on its own, Kohn packaged the gene into a virus, which would ferry the new message into the cells.