What Causes an MS Plaque?

The typical MS plaque seen in patients who have died early in their illness or who have had brain biopsies is composed of a mixture of lymphocytes with many more macrophages, without antibody.

The macro-phages in the plaque contain myelin within their cell bodies in various stages of digestion. Some axons are damaged, but they are relatively preserved as compared with myelin. After the initial insult by these cells, scar-ring begins. This process varies greatly from one individual to another.

Curiously, the macrophages contain hormones like brain-derived nerve growth factor that should stimulate repair. The macrophage also secretes another hormone that stimulates scarring (T-cell growth factor beta-1). The invading cells seeking to remove some unknown enemy virus or protein seem prepared to help in rebuilding the damaged tissue. Later in the development of the plaque, scarring occurs. It is this scarring that makes the plaque hard (sclerotic).

In summary, the plaque is an area of intense inflammation with myelin damage where the nerve fibers are relatively preserved and show variable amounts of scarring.