Does Parkinson's result in a breakdown of the body being able to cure itself?

No. No spontaneous "cures" of parkinsons disease occur. The disease however may fail to progress for long periods of time but once initiated, never goes away.
Yes. Parkinson disease is a degenerative disorder of the nervous system that affects cells in the brain associated with movement. Once the cells are lost they cannot be regenerated and you will see a decline in motor function. Medications, surgery and other management can provide relief and sometimes improve symptoms, but the cells cannot be replaced and the disease cannot be fully cured.