How stress lowers our immune defenses

The link between stress and weakened immune defenses has already been established in several studies, but the process remains poorly understood. How can stress affect our immunity and make us more vulnerable? Sophie Ugolini, Inserm research director at the Center for Immunology at Marseille-Luminy, and her colleagues from CNRS and Aix-Marseille University have just discovered the mechanisms of this biological reaction in our body. Their work has been published in the Journal of Experimental Medicine.

We know that when infected, stress is associated with reduced efficiency of the immune defense system. To explain it, the researchers looked at receptors expressed on the surface of many cells in the body (including immune cells) and which are specific to the stress hormones, adrenaline and norepinephrine, which are called β2-adrenergic receptors.

Stress decreases resistance of mice

They firstmimicking a situation of chronic stress in mice by administering for seven days a molecule which, like stress hormones, stimulates β2-adrenergic receptors ”, Inserm explains in a press release. Then the researchers exposed the rodents to a virus of the herpes family, the cytomegalovirus MCMV.

They discovered that the mortality rate of “stressed” mice was then higher than that of mice that had not received the “stress molecule” (90% versus 50%). In short, the stress felt at the time of their exposure to the cytomegalovirus MCMV considerably weakened their immune defenses.

In a second step, the researchers assessed the resistance of rodents to the virus in the absence of these receptors. “For this, they exposed to cytomegalovirus mice genetically modified to be devoid of β2-adrenergic receptors. In these animals, the stress hormones could no longer bind to β2 receptors and therefore could no longer act. ”

They were much more resistant to viral infection: there was 90% survival against only 50% for control mice. “These first results therefore suggest that stimulation of β2-adrenergic receptors by stress hormones is responsible for the weakening of the immune system in situations of psychological stress ”, write the researchers.

Towards a new therapeutic path?

“We have experimentally confirmed that the stress hormones that bind to β2-adrenergic receptors reduce the immune response and that this involves a decrease in the production of certain inflammatory cytokines, required for the elimination of viruses ”, specifies Sophie Ugolini.

According to the researcher, this work could lead to new therapeutic ways to treat stress. “By targeting the β2-adrenergic receptor, it would indeed be possible, in certain pathological contexts, to remove the immune brakes caused by a state of stress. ”

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