Immune response linked to Parkinson’s disease : Parkinson’s disease is a degenerative brain disorder that develops when nerve cells in the brain become impaired and eventually die. As these brain cells die, people with Parkinson’s disease may start experiencing involuntary shaking, muscle stiffness, slowed movements, problems with balance, and other symptoms. At first, only a tremor in one hand may be noticeable. As the disease advances, people may have trouble talking, getting dressed, and walking. There’s no cure for the disease, but medicines or surgery can help with managing symptoms.