A 12 year old boy named David was born without an immune system. He underwent a bone marrow transplant in order to correct the deficiency. Up to that point he had spent his entire life in a plastic bubble in order to prevent exposure to common germs, bacteria, and viruses that could kill him. He lived without ever knowing human contact. When asked what he'd like to do if and when released from his protective bubble, he replied, "I want to walk barefoot on grass, and touch my mother's hand."