Research suggests that repeated stress leads to an excess of white blood cells in the spleen, and these white blood cells can send behavior altering messages to the brain long after the stress experience.
This relationship between the brain and the immune system has been observed in a recent laboratory study with mice, and it may help explain the long term consequences of stress in humans.
“We found that immune cells in the spleen can contribute to chronic anxiety following psychological stress,” said lead study author Daniel McKim, an Ohio State University grad student. “Our findings emphasize the possibility that the immune system represents a novel therapeutic target for the treatment of mental health conditions.”
The researchers - which include McKim’s advisors, professors John Sheridan, and Jonathan Godbout - determined that the immune cell alterations in mice caused by stress persist for nearly a month following the stress experience.
Stress seems to trigger an immediate release of stem cells from the bone marrow to the spleen. In the spleen the stem cells change into white blood cells, called monocytes, which expand over time. This turns the spleen into a cache of inflammatory cells that Godbout likens to a “stress memory.”
The investigators now realize the spleen is an intrinsic part of the sensitization occurring in mice after prolonged stress that eventually manifests as cognitive problems, including anxiety.
The goal of their research is to understand the intricate interplay of immunity and stress in animals undergoing “repeated social defeat,” and using the knowledge to boost the well-being of psychologically stressed people. To that end, Sheridan and Godbout are piecing together the bi-directional communications going on between the brain and the body.
“Maybe anxiety is a good thing for survival - it’s beneficial evolutionarily - but the issue becomes what happens when that system is put into overdrive. That’s when it gets problematic,” says Godbout.
Source: Science Daily
Photo credit: David Goehring