Multiple sclerosis causes disabling neurological symptoms, but the mechanism behind the disease has not been clear. An imaging study in mice now reveals that a specific set of immune cells may be the culprit in triggering neuronal injury.

Volker Siffrin and Frauke Zipp at Johannes Gutenberg University in Mainz, Germany, and their group used in vivo microscopy to observe immune cells and neurons in the brains of mice with autoimmune encephalomyelitis, an animal model of multiple sclerosis. The authors found that a type of white blood cell called a Th17 cell directly interacts with neurons to form synapse-like contacts. This interaction increases calcium levels in the neurons — an early sign of cell damage. When the researchers blocked key receptors on the neurons, calcium levels subsided somewhat, showing that the damage may be at least partially reversible.

Immunity 33, 424–436 (2010)