Having stressed out ancestors might improve immune response to stress, say researchers

If your ancestors were frequently exposed to stress, there is a chance that you might have developed an improved immune response to stress, a recent study suggests.

The research suggests that family history should be considered to predict or understand the health implications of stress. Having ancestors who were frequently exposed to stressors can improve one's own immune response to stressors, according to Penn State researchers.

"Prolonged stress typically suppresses immune function within an individual. For example, we often think of ourselves as more likely to get a cold when we're stressed," says Tracy Langkilde, lead author of the study.

As part of the study, the researchers found that lizards whose ancestors lived in low-stress environments experienced suppressed immune function when they were exposed to prolonged stress.

"But for lizards whose ancestors lived in high-stress environments, those animals had more robust immune systems when they were exposed to stress. So the immune response to stress actually is dependent upon the environment experienced by previous generations," adds Langkilde.

The researchers believe that the results may be similar in other animals, perhaps even in humans. Of course, various animals are subjected to different kinds of stressors.

Of course, various animals are subjected to different kinds of stressors. In these lizards, she said, stress is often the result of attacks by fire ants, an invasive species that occur in the southeastern United States and is spreading northward and westward.

To investigate the immune consequences of stress on animals with different heritages, the team captured pregnant females from the wild from two different kinds of environments-one that had been invaded by fire ants 60-to-70 years prior, or the equivalent of 30-to-40 lizard generations, and one that had not yet been invaded by fire ants.

The researchers raised the offspring of the captured females in high- and low-stress environments until they were adults. They created high-stress conditions by either exposing the lizards to fire ants or by dosing them every week with the stress-relevant hormone corticosterone dissolved in oil.

A paper describing these results appeared in the Journal of Experimental Biology.

Once the lizards reached adulthood-approximately 1-year-old-the scientists assessed the animals' immune function by measuring the ability of their blood plasma to hold a foreign protein in suspension.

"We found that offspring of lizards from high-stress environments had suppressed immune function while offspring of lizards from low-stress environments had enhanced immune function when they were exposed to stress relevant hormones during their own lifetime," said McCormick.

"This change is likely adaptive, as an enhanced immune response in the face of stress should also enhance survival in the presence of frequent attack by fire ants." McCormick noted that understanding how species respond to stress can help in their management.