Multiple sclerosis, or MS, is a chronic disease of the central nervous system in which the myelin sheath and nerve axons in certain areas of the brain are destroyed. Research into the etiology of the disease is constantly being conducted, and although it is not certain, it is believed that the T lymphocytes used by the body for immune functions may have an important role in the disease process — it is a possibility that in the future, it will be categorised as both a neurological disease and an autoimmune disease.