Parkinson's gets progressively worse
Rogue immune cells entering the brain may contribute to the development of Parkinson's disease, say scientists.
A French study in diseased mice revealed the cells accumulating in brain tissue, and mice bred to lack them did not fall ill as quickly.
The researchers suggested that the cells could be targeted using drugs.
A UK charity said the findings, published in the Journal of Clinical Investigation, did not yet prove that this approach would work.
About 120,000 people in the UK have Parkinson's disease, a progressive brain condition which causes symptoms such as tremor and difficulty moving.
This is caused by the death of nerve cells which produce the chemical dopamine, which helps coordinate movements.
Previous research had suggested a link between inflammation in the brain and the condition, pointing the finger at one of the body's own immune responses.
The researchers from the INSERM institute in Paris looked for the presence of a particular type of immune cell called a "T-cell" in the brain tissues directly affected by Parkinson's.
They found the cells gathering both in human brain samples taken from Parkinson's patients after death, and at an earlier stage in mice bred to develop the disease.
When mice lacking these immune cells were studied, the rate of nerve cell death was significantly slower.
The researchers said that this was enough evidence to start considering the possibility of using drugs to reduce this kind of immune response in patients with Parkinson's, in the hope that this might slow the progress of the disease.
However, a spokesman for the Parkinson's Disease Society said that the research did not exclude other causes for the illness.
"This study has shown that the Parkinson's developed at a slower rate in mice lacking specific immune cells, which suggests that these cells do play a role in the development of the condition.
"However, the study doesn't determine at what stage of the disease the inflammation occurs. Therefore, the potential for anti-inflammatory treatment is difficult to determine."
He added: "It is also important to remember that as the study was done using mice, it doesn't provide a precise model for what happens in the human brain."