Multiple sclerosis, a debilitating neurological disease, is triggered by self-reactive T cells that successfully infiltrate the brain and spinal cord where they launch an aggressive autoimmune attack against myelin, the fatty substance that surrounds and insulates nerve fibers. In their latest study, researchers report that these disease-causing autoimmune T cells are lured into the nervous system by monocytes and macrophages, a subset of immune cells better known as the immune system's cleanup crew.