Male and female mice use different types of immune cell to process chronic pain.

Studies of male mice have shown that immune cells called microglia in the spinal cord have an important role in chronic pain. To see whether this is the same in female mice, a team led by Jeffrey Mogil at McGill University in Montreal and Michael Salter at the University of Toronto, both in Canada, induced chronic pain in both sexes. The team then used drugs or antibodies to reduce microglia function. Whereas pain responses were reduced in the males, females were unaffected and instead recruited a different type of immune cell, called a T cell. This difference was linked to testosterone, which could make T cells less able to mediate pain in the males, leading to their use of microglia instead.

Nature Neurosci. (2015)