Short-term stress can enhance immunity

2019-03-02 03:12:02

By Melissa Lee Phillips Mice that are briefly stressed out before receiving a vaccine develop a better immune response than mice under no psychological stress, a new study reveals. This advantageous immunity persists for at least nine months – a good chunk of a mouse lifespan – and is likely to arise because an acutely stressed immune system develops better memories for foreign invaders, the study’s authors suggest. “Stress can influence different features of the immune response in different ways, sometimes improving and sometimes suppressing” this response, says Monika Fleshner, of the University of Colorado at Boulder, US. While chronic stress suppresses “nearly every feature of the immune system,” acute stress can enhance some features, she says. Firdaus Dhabhar and Kavitha Viswanathan at Ohio State University, US, injected mice with a small amount of protein called keyhole limpet hemocyanin (KLH), which triggers the body’s immune response in a way similar to many proteins, according to Dhabhar. Half of the mice were put in small, unfamiliar wire cages for two and a half hours immediately before receiving their immunisations, while the other half stayed in their regular cages. Nine months later, the researchers injected the animals with KLH at a different skin site. Mice that had been confined before being immunised developed much more skin inflammation than did the non-stressed mice – a sign that their bodies’ immune systems responded more intensely to the new injections. The researchers show that many more immune cells rushed to the injection sites in mice that had been stressed. The researchers think that acute stress somehow encourages activity of immune cells called memory T cells. Memory T cells remain in the body after infection or vaccination and “remember” the chemical components of the invader. If short-term stress enhances the activity of memory T cells after a KLH vaccine, then these cells will mount a better defence when KLH is injected again. But according to Bruce Rabin at the University of Pittsburgh Medical Center, US, acute stress is unlikely to enhance human immune responses. “In humans, even a short stressor is suppressive to the immune system,” he notes. Fleshner differentiates between mild and severe stressors: In mice – and probably in humans – short-term stressors can impair the immune response if they are severe, she says. Mild stressors like being placed in an unfamiliar cage activate a different stress response than severe stressors like being shocked, she says. Journal reference: American Journal of Physiology – Regulatory, Integrative, and Comparative Physiology (DOI: