A study in the journal Nature has found evidence that Parkinson’s disease is related to the immune system.

It’s thought it may be something called an autoimmune disease, where your body’s immune system attacks healthy cells by mistake. It’s possible that the death of neurons caused by Parkinson’s could therefore be prevented by dampening the body’s immune response.

“Our findings raise the possibility that an immunotherapy approach could be used to increase the immune system’s tolerance for alpha-synuclein, which could help to ameliorate or prevent worsening symptoms in Parkinson’s disease patients,” said Dr Alessandro Sette, study co-leader from the Center for Infectious Disease at the La Jolla Institute in California, in a statement.

The team made their findings by exposing blood samples from 67 Parkinson’s disease patients and 36 age-matched healthy people to bits of alpha-synuclein and other proteins found in neurons. While the control group saw little immune cell activity, the blood samples of the other group showed a strong response.

The cause may be that neurons in people with Parkinson’s disease are not able to get rid of abnormal alpha-synuclein. This means the protein can get mistaken as a pathogen and subsequently attacked.

"The idea that a malfunctioning immune system contributes to Parkinson's dates back almost 100 years," said David Sulzer from Columbia University Medical Center (CUMC), who led the study. "But until now, no one has been able to connect the dots. Our findings show that two fragments of alpha-synuclein, a protein that accumulates in the brain cells of people with Parkinson's, can activate the T cells involved in autoimmune attacks.”

At the moment, it’s not clear if the immune response is the initial cause of Parkinson’s or instead a contributing factor to worsening symptoms. But it could help scientists more easily diagnose Parkinson’s in people at an earlier stage of the disease.

A previous study in 2014 by Dr Sulzer and colleagues provided evidence that neurons were vulnerable to autoimmune attacks. Previously, they had been thought to be protected, but proteins on their cell surface were found to play a role in helping the immune system find foreign substances.

This recent study showed that T cells, a type of white blood cell that play a key role in immunity, could be the culprit. If damaged alpha-synuclein proteins build up, something that happens during Parkinson’s disease, then the T cells can be tricked into thinking dopamine neurons are foreign.

Dopamine neurons play a number of roles, including carrying signals for physical activity. Thus, their loss can be linked to some of the symptoms of Parkinson’s disease, such as shaking or reduced movement.