What condition involves the body’s immune system attacking parts of the nervous system?

The correct choice is multiple sclerosis because it is a chronic autoimmune disease in which the body's immune system mistakenly attacks the myelin sheath that encases nerve fibers in the central nervous system. This leads to communication problems between the brain and the rest of the body, causing a wide range of neurological symptoms.

In contrast, Guillain-Barré syndrome, while also involving the immune system, primarily affects the peripheral nervous system and is typically characterized by rapid-onset muscle weakness. Alzheimer's disease is not an autoimmune condition but rather a progressive neurodegenerative disorder that primarily affects memory and cognitive function. Huntington's disease is a genetic disorder that causes the progressive breakdown of nerve cells in the brain and is not related to the immune system attacking the nervous system.