On September 14, 1990, researchers at the U.S. National Institutes of Health performed the first approved gene therapy procedure on four-year old Ashanti DeSilva, born with severe combined immune deficiency. Doctors removed her white blood cells, let the cells grow in the lab, inserted the missing gene into the cells, and then infused the genetically modified blood cells back into the patient's bloodstream. Laboratory tests have shown that the therapy strengthened Ashanti's immune system. She no longer has recurrent colds, and has been allowed to attend school.