Scientists can reboot a human immune system by destroying it and then transplanting new stem cells. This is a promising line of research given what happens to the immune system with aging, but the present focus is curing autoimmune disease: researchers "appear to have reversed the neurological dysfunction of early-stage multiple sclerosis patients by transplanting their own immune stem cells into their bodies and thereby 'resetting' their immune systems. ... [researchers] treated patients with chemotherapy to destroy their immune system. They then injected the patients with their own immune stem cells, obtained from the patients' blood before the chemotherapy, to create a new immune system. ... We focus on destroying only the immune component of the bone marrow and then regenerate the immune component, which makes the procedure much safer and less toxic than traditional chemotherapy for cancer ... After the transplantation, the patient's new lymphocytes or immune cells are self-tolerant and do not attack the immune system. ... In MS the immune system is attacking your brain. After the procedure, it doesn't do that anymore."