This research wants to know if medicines called immunosuppressive drugs can change how Parkinson's disease, a brain disorder that affects movement, develops. These drugs are usually given to help with other illnesses by calming the immune system. The study will include two groups: people with Parkinson's who take these drugs, and those who don't.

Participants need to visit the hospital once for about an hour. During this visit, doctors will check how Parkinson's affects their movement. It's important that participants don't take their Parkinson's medicine on that day. They'll also answer questions about their symptoms, give a small blood sample, and talk about their medical history, especially their use of immunosuppressive drugs.

• Only one hospital visit is needed, lasting about one hour.
• Participants will not take their Parkinson's medicine on the day of assessment.
• No compensation is mentioned for participation.

Before joining, participants must give consent, which means they agree to take part after understanding the study's details. People with certain health issues, like advanced cancer or severe heart problems, cannot join.