Washington: A new study has showed that chronic stress alters gene activity in immune cells before they reach the bloodstream.
With these changes, the cells are primed to fight an infection or trauma that doesn't actually exist, leading to an overabundance of the inflammation that is linked to many health problems.
Ohio State University scientists made and their colleagues from other institutions, testing blood samples from humans living in poor socioeconomic conditions, found that similarly primed immune cells were present in these chronically stressed people as well.
Co-lead author John Sheridan, professor of oral biology in the College of Dentistry and associate director of Ohio State's Institute for Behavioral Medicine Research (IBMR),sa di that the cells share many of the same characteristics in terms of their response to stress.
He said that there is a stress-induced alteration in the bone marrow in both our mouse model and in chronically stressed humans that selects for a cell that's going to be pro-inflammatory.
Sheridan and colleagues have been studying the same mouse model for a decade to reveal how chronic stress - and specifically stress associated with social defeat - changes the brain and body in ways that affect behavior and health.
The mice are repeatedly subjected to stress that might resemble a person's response to persistent life stressors. In this model, male mice living together are given time to establish a hierarchy, and then an aggressive male is added to the group for two hours at a time.
This elicits a "fight or flight" response in the resident mice as they are repeatedly defeated by the intruder.
Under normal conditions, the bone marrow in animals and humans is making and releasing billions of red blood cells every day, as well as a variety of white blood cells that constitute the immune system.
In this work, the researchers compared cells circulating in the blood of mice that had experienced repeated social defeat to cells from control mice that were not stressed. The stressed mice had an average fourfold increase in the frequency of immune cells in their blood and spleen compared to the normal mice.
The study has been published in the journal Proceedings of the National Academy of Sciences.