WHAT doesn鈥檛 kill you makes you stronger, at least when it comes to stress and immune cells. Mice that received a cocktail of immune cells from bullied mice appeared to experience a mood boost. The unexpected discovery may have implications for treating depression.
We know that prolonged bouts of stress take their toll on the immune system. That leaves us susceptible to .
Most research on the link between immune health and mood has focused on the innate branch of the immune system 鈥� the cells that mount the first response to pathogens, says at the National Institutes of Health in Bethesda, Maryland. His team wondered if there might also be a role for the adaptive branch of the immune system, which 鈥渓earns鈥� about a pathogen in order to respond rapidly the next time it appears.
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To find out, the team introduced an aggressive competitor mouse into the cages of male mice. 鈥淭hese mice are like bullies,鈥� says Herkenham. Two weeks later, the bullied mice seemed depressed: they cowered in dark corners and seemed uninterested in the scent of a female.
The team extracted their adaptive immune cells and injected them into another set of mice bred to lack these cells. This meant that the recipient mice essentially acquired the adaptive immune system of the bullied ones.
If anything, Herkenham thought the recipients would become depressed, too. But the opposite happened: the cells appeared to have 鈥渁ntidepressant-like effects鈥�, he says. The mice spent more time exploring open areas and were more interested in females compared to similar mice that didn鈥檛 receive the injection (Journal of Neuroscience, ).
The team also injected the cells into a strain of mice known for their unresponsiveness. 鈥淭hese mice are rarely used in research because they don鈥檛 do anything 鈥� they just sit in a corner,鈥� says Herkenham. The mice were soon running around, exploring their surroundings with abandon. 鈥淚t was like a personality change,鈥� he says.
Herkenham thinks that adaptive immune cells may cope with stress by building up a sort of mood-boosting resilience, although he doesn鈥檛 know how this happens. What鈥檚 unclear is why the donor mice didn鈥檛 eventually become better at coping with their bullies, and why .
In these cases, the adaptive immune system appears to be held back from exerting its beneficial effects 鈥� and the innate branch of the immune system may be to blame, says Herkenham. It鈥檚 already known that . Perhaps the two arms of the immune system are in effect battling it out to dominate mood.
聯The two arms of the immune system are in effect battling it out to dominate our mood聰
George Slavich at the University of California, Los Angeles, says it would be premature to call the adaptive immune system 鈥渁ntidepressive鈥�. 鈥淭he immune system is extremely complex and these two branches interact in many ways,鈥� he says.
The team now hope to disentangle what is going on and explore whether reprogramming adaptive immune could hint at a new treatment for depression.
This article appeared in print under the headline 鈥淗ow ironic: eau de stress can be an antidepressant鈥�
