Immune system blocks Alzheimer's2nd June 2008
Turning off a part of the immune system could be helpful in clearing away harmful brain deposits in patients with Alzheimer's disease, resulting in improved memory, new research in the United States has shown.
According to the study in the journal Nature, the body's immune system could be harnessed to fight back against Alzheimer's disease, researchers concluded after a study in mice.
Further research is needed to determine whether the process also works in humans, in whom Alzheimer's gradually attacks memory capacities and eventually the ability to live normally.
The damage in the brain is caused by a build-up of "amyloid plaques", leading to a number of research enquiries focusing on possible ways to remove those plaques from brain cells.
Therapies which successfully achieve this may be able to delay or even reverse the progress of Alzheimer's, for which some drugs are available which delay the disease's progress in some patients, but for which no cure has yet been found.
It is currently very hard to develop a drug which is able to cross the blood-brain barrier, a protective system which prevents large molecules from getting into the brain from the bloodstream.
The research team, co-authored by Yale University professor Richard Flavell, used genetic engineering to block an immune system response in mice, but only in cells outside the brain.
Initially, they had expected to see a worsening of the Alzheimer's, expecting the immune response of the mice to be forced into overdrive, causing too much inflammation inside the brain.
Instead, 90% of the plaque material disappeared from the brains of the mice, and the animals' performance in memory tests using mazes was significantly improved after the change.
Immune cells called macrophages, which drift through the body engulfing potentially harmful intruders like bacteria or debris, instead turned their attention to the brain-damaging plaques in the genetically altered mice.
And when the animals' memories were tested using mazes, significant improvements were found.
Flavell described the effect as "like a vacuum cleaner" which sucked up the plaques.
Co-author Terence Town said the possibility could now be raised of a drug based on this technique to treat Alzheimer's in people.
Town said that if results from the study in mice engineered to develop Alzheimer's-like dementia were supported by studies in humans, it might now be possible to develop a drug that could be introduced into the bloodstream to cause peripheral immune cells to target amyloid plaques.
Experts said increasing numbers of studies were now looking at the role played by inflammation in the brain and Alzheimer's, suggesting inflammatory reactions might play a key role in the disease's development and progression which had previously been overlooked.
They called for further research to find the best potential drug to stop the inflammatory reaction and to investigate whether the same effects would occur in people
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