Patients were given a drug which encourages stem cells to move from the bone marrow into the bloodstream, where they were removed from the body.High-dose chemotherapy was then administered to kill all immune cells, before the patient’s own stem cells were put back into the body to “reset” the immune system.Nearly three in four (73 per cent) patients with relapsing MS – where the disease flares up before symptoms improve – found their symptoms did not worsen for five years after having AHSCT, compared with one in three patients with progressive MS, the more severe variant of the disease. We previously knew this treatment reboots or resets the immune system but we didn’t know how long the benefits lastedDr Paolo Muraro, Imperial College London The disease is caused by the immune system malfunctioning and mistakenly attacking nerve cells in the brain and spinal cord.It leads to problems with movement, vision, balance and speech.The treatment, autologous hematopoietic stem cell transplantation (AHSCT), was given to patients with advanced forms of the disease who had failed to respond to other medications.A similar approach has been trialed on people with certain forms of cancer, with encouraging early results.Dr Paolo Muraro, the new study’s lead author, said: “We previously knew this treatment reboots or resets the immune system but we didn’t know how long the benefits lasted.”In this study, which is the largest long-term follow-up study of this procedure, we’ve shown we can ‘freeze’ a patient’s disease – and stop it from becoming worse, for up to five years.”The researchers noted, however, that the nature of the treatment, which involves aggressive chemotherapy, carried “significant risks”.The chemotherapy deactivates the immune system for a short period of time, which can lead to greater risk of infection – of the 281 patients who received AHSCT, eight died in the 100 days after treatment.The treatment works by destroying the immune cells responsible for attacking the nervous system. A multiple sclerosis treatment which “resets” the immune system has been found to “freeze” progression of the disease in nearly half of patients, according to scientists.A study led by Imperial College London found that 46 per cent of patients who underwent the treatment did not suffer a worsening of their condition for five years.The treatment could give hope to the estimated 100,000 people in the UK who are affected by multiple sclerosis (MS), for which there is currently no cure. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.