J. Exp. Med. doi:10.1084/jem.20092749 (2010)

The primary job of natural killer (NK) cells, a type of immune cell, is to destroy host tissue infected by pathogens. The cells are also thought to boost autoimmunity under certain circumstances by acting on other immune cells in the lymph nodes. Fu-Dong Shi at St Joseph's Hospital and Medical Center in Phoenix, Arizona, and his colleagues now report that NK cells have a stronger effect on autoimmunity in the central nervous system.

The researchers studied a mouse model of multiple sclerosis, a disease in which the immune system attacks myelin, the protective sheath surrounding nerve fibres in the brain and spinal cord. They found that NK cells limit inflammation and the immune response against myelin antigens. Increasing the number of NK cells in the central nervous system protected the animals from disease, whereas limiting the cells' numbers made symptoms worse. The researchers speculate that drugs used to treat multiple sclerosis may exert their positive effect by increasing NK cell numbers.