The study took place in France and used mice with a form of Parkinson's disease. The immune cells were shown to accumulate in the mice's brain cells. Mice bred to lack this immune cell did not fall ill as quickly. The study was published in the Journal of Clinical Investigation.
The researchers from the INSERM institute in Paris looked for the presence of T-cells 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.
