Autoimmune diseases are triggered by immune cells that attack the body's own tissue. In multiple sclerosis (MS) immune cells succeed in invading nervous tissue and sparking off a destructive inflammation there which can be accompanied by neurological deficits such as paralysis and somatosensory defects.
A healthy brain is practically free from immune cells, because the nervous system is separated from the rest of the body via specialised blood vessels that prevent immune cells from entering it from the blood. Up to now it has been unclear how in MS immune cells can overcome this barrier and seemingly pass unhindered into the brain tissue.
A research team, initially at the Germany's Max Planck Institute for Neurobiology in Martinsried, near Munich, and later at the University of Göttingen, could now show that these disease-causing immune cells are programmed in the lung to be more motile and to efficiently break through blood vessel barriers.
Specialised immune cells, so-called T cells, are held to be the cause of MS. Even though nearly every healthy human harbours potentially disease-causing T cells in his or her immune system, only around 0.1 per cent of the population actually develops a manifest MS.
One of the reasons for this is that normally T cells are stopped from entering the brain by a virtually impermeable vascular barrier separating the central nervous 2/3 system from the blood circulation.
''Earlier work in experimental MS research showed that when T cells are pre-activated outside nervous tissue they are very well able to pass into the brain and trigger MS-like symptoms there'', explains Alexander Flügel, now head of the Department of Neuroimmunology and the Institute for Multiple Sclerosis, University Medical Center, Göttingen. ''However, we wanted to find out exactly where in the body these T cells are activated and exactly which properties enable them to overcome the bloodbrain barrier.''