Multiple sclerosis (MS) is caused by immune cells that activate a cascade of chemicals in the brain, attacking and degrading the insulation that keeps neuronal signals moving. These chemicals, called cytokines, drive the inflammation in the brain, attracting more immune cells, and causing the debilitating disease marked by loss of neurological function. Researchers have now discovered the role of a major cytokine in multiple sclerosis that could be a target for new therapy against the disease.