Neurotransmitter-Regulated Immunity
Nerve signals control T cell responses, helping to explain inflammation and stroke.
By Rachel Nuwer | September 15, 2011

http://the-scientist.com/2011/09/15/...ated-immunity/

Neurotransmitters may play a bigger role in immunity than scientists had realized. In two papers published today (September 15) in Science Express, immunologists identify neurotransmitters as key players in two previously mystery-shrouded defense mechanisms: how the nervous system body puts the brakes on an overenthusiastic inflammatory response, and the reasons behind post-stroke infections.

“These connections between the brain and immune system in both health and disease are very intriguing,” said Lawrence Steinman, a professor of neurology ... The findings could have implications for the treatment of inflammatory disorders and stroke patients, he added.

The immune system is designed to protect the body from infection and injury, but an overactive immune response can damage organs or lead to inflammatory diseases. The vagus nerve connects the brain to the body and controls inflammatory response. One molecule in particular, the neurotransmitter acetylcholine, is released by the vagus nerve to slow the immune response before it causes collateral damage. In the spleen, for example, acetylcholine is necessary for blocking the production of dangerous amounts of inflammatory molecules like cytokines, but the details of how it worked was unclear.

Kevin Tracey, an immunologist at the Feinstein Institute for Medical Research in Manhasset, New York, discovered the “missing piece” for how the vagus nerve orchestrates immunity. Tracey and colleagues found that T cells in mouse spleens are actually releasing acetylcholine themselves after receiving a signal from the vagus nerve, playing a critical role in blocking inflammation. Though T cells are part of the immune system, in this context they’re essentially functioning as a neuron, Tracey said. “It’s remarkable.” Though the idea that immune cells can make neurotransmitters is not a new story, Tracey added, no one has ever shown that nerve signals initiate their release, and in turn play a protective anti-inflammatory role against disease...