US soldier undergoes double arm transplant

In 2009, Morocco lost his arms and legs in an explosion while serving in Iraq. Recently, he underwent a successful double arm transplant. The surgery involved shaping donor bones, tagging muscles and tendons, and connecting blood vessels and nerves. A bone marrow infusion was given to reduce anti-rejection drugs. Morocco is one of only seven people in the US to have had this surgery.

What was the purpose of the bone marrow infusion given to Morocco?

How many people in the US have successfully undergone double arm transplant surgery, including Morocco?