Parkinson’s disease (PD), a condition usually associated with the nervous system, appears to have a connection to the immune system as well. So much so that scientists are starting to think that PD could be more like an autoimmune disease than they thought.
Neuroscience meets immunology in a new study funded by the National Institute of Neurological Disorders and Stroke (NINDS). A team of researchers from both the East and West coasts analyzed blood samples – 67 from individuals with PD and 36 from healthy people. From the blood samples they could extract immune cells, and then they mixed in proteins called alpha-synucleins that lead to cell death. Alpha-synuclein proteins are infamously found in the brains of people with PD.
Zeroing in on the activity of the samples’ T cells, researchers saw that these specialized adapted immune system cells responded greater to alpha-synuclein when they came from the blood of someone with PD, more so than T cells from a healthy person.
They saw two alpha-synuclein regions that particularly attracted the attention of T cells: one region associated with mutations linked to PD, and one that undergoes a chemical change leading to the accumulation of alpha-synuclein in the brain that characterizes PD. Four genetic variations were found to have links to PD T cells reacting to alpha-synuclein, and at least one of the genetic variations were found in more than half of people with PD.
What does this mean? PD could be more like an autoimmune disease than scientists realized, if T cells are indeed targeting the brain’s healthy cells in a way that contributes to characteristics of PD. In a more typical situation, T cells would be responsible for targeting cells from pathogens - like bacteria or viruses - or cancer cells. And it may not just be PD; the immune system could have a similar relationship with other neurodegenerative disorders.
"As we age, proteins throughout the body undergo various molecular modifications,” explained David Sulzer, PhD, from Columbia University. If they become unrecognizable, the immune system may start going after them, thinking they may be dangerous invaders."
"These findings expose a potential biomarker for PD that may someday help in diagnosing the disease or be used to evaluate how well treatments are working," explained Alessandro Sette, PhD, from the La Jolla Institute for Allergy and Immunology in California.
Parkinson’s disease leads to tremors, muscle stiffness, loss of balance, slow movement as more and more dopamine-producing brain cells begin to die. About one million people in the United States are currently living with PD.
The present study was published in the journal Nature.