Hyperactive immune system offers window to the brain in degenerative disease

HD is a fatal, incurable genetic neurological disease that usually develops in adulthood and causes abnormal involuntary movements, psychiatric symptoms and dementia. The new research by UCL scientists, working in close partnership with scientists from King's College London and institutions in Sweden, the USA and Canada, showed that abnormally high levels of molecules called cytokines - key to the body's immune response - were present in the blood of people carrying the HD gene many years before the onset of symptoms.

Finding these cytokine levels in the blood of HD gene carriers so long before they exhibit symptoms could be an important clue to some of the earliest changes caused by the HD gene. The combinations and levels of cytokines, easily measured from a blood test, could be useful markers to help measure the severity of HD, making it easier and quicker to test new drugs.

In addition, the team showed that white blood cells from HD patients were hyperactive, due to the presence of the abnormal HD gene inside the cell. This hyperactivity was also seen in microglia (the brain's immune cells) suggesting that abnormal immune activation could be one of the earliest abnormalities in HD, and that its signature in the blood could offer a glimpse into the effects of the disease in the brain. Abnormal immune activation could be a target for future treatments aimed at slowing down HD.

Dr Sarah Tabrizi, UCL Institute of Neurology, led the research. She said: "Finding increased cytokines in the blood was interesting, but the idea that the HD gene could be causing immune overactivity directly from within the white blood cells is important, because if the same thing is happening in the brain, cells that are there to protect neurons could be damaging them instead."

"It looks like we've unearthed a new early pathway by which the HD gene could cause damage, through abnormal overactivity of the immune system. What's more, this new pathway is quite easy to detect in the blood of patients, so we may have found a unique window from the blood into what the disease may be doing in the brain."

HD is currently incurable and no effective treatments exist to slow it down. It affects an estimated 4 to 10 per 100,000 people of European ancestry, and patients usually die within 20 years of the start of symptoms. The disease is caused by a single known genetic mutation, and each child of a carrier of the mutation has a 50 per cent chance of inheriting the disease.

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Notes for Editors

1. Journalists seeking more information, or an interview with Dr Sarah Tabrizi, can contact Ruth Metcalfe in the UCL Media Relations Office on tel: +44 (0)20 7679 9739, mobile: +44 (0)7990 675 947, out of hours: +44 (0)7917 271 364, e-mail: r.metcalfe@ucl.ac.uk

2. The paper 'A novel pathogenetic pathway of immune activation detectable before clinical onset in Huntington's disease' is published online ahead of print today in the Journal of Experimental Medicine. For copies of the paper, please contact Media Relations using the details above.

3. The paper's authors are from Lund University, Sweden; UCL Institute of Neurology and UCL Department of Haemotology; University of British Columbia, Canada; University of Washington, US and King's College London.

4. Funding for this study was provided by CHDI (previously the High Q Foundation), Department of Health, the Medical Research Council (MRC), the Wellcome Trust, the Canadian Institutes for Health Research and the Huntington Society of Canada.