People whose ancestors were exposed to stressors improved their immune response to stress

Having ancestors who have been frequently exposed to stressors can improve their own immune response to stressors, according to Penn State researchers. The results suggest that family history should be taken into account in predicting or understanding the health implications of stress.

"Prolonged stress usually suppresses immune function in an individual," said Tracy Langkilde, professor and chief of biology at Penn State. "For example, we often think that we are more likely to have a cold when we are stressed." We found that lizards whose ancestors lived in low-stress environments had suppressed immune function when we exposed them to a Prolonged stress But for lizards whose ancestors lived in highly stressed environments, these animals had a stronger immune system when exposed to stress, so the immune response to stress depends on the environment of previous generations. "

According to Langkilde, the team has been working on fencing lizards (Sceloporus undulatus), but thinks that the results could be similar in other animals, perhaps even in humans. Of course, various animals are subjected to different types of stress. According to her, in these lizards, stress is often the result of attacks of live ants (Solenopsis invicta), an invasive species found in the southeastern United States and spreading northward and upwards. Where is.

"Fire ants can sting and poison lizards, which is stressful and potentially fatal for lizards," said Gail McCormick, a graduate student at Langkilde Lab at the time of the research. "These attacks break the skin of lizards, making them vulnerable to infections, so it's probably a bad idea to suppress immune function in response to stress when the predominant stressor, fire ants, already induce an immune response through Due to an injury, it turns out that lizards whose ancestors originate from areas where fire ants have a better immune response to stress, which can contribute to their survival. "

To study the immune consequences of stress on different animal heritages, the team captured pregnant females in the wild in two different types of environments – one having been invaded by fire ants. 60 to 70 years ago, or the equivalent of 30-to-40 generations of lizards, and one that has not yet been invaded by fire ants.

The researchers raised the offspring of females captured in high or low stress environments until they were adults. They created high stress conditions by exposing the lizards to ants or dosing them weekly with corticosterone, a hormone useful for stress, dissolved in oil.

"This mix soaks lizard skin as a lotion, causing an increase in their blood levels of corticosterone that mimics their physiological response to being pursued or attacked by fire ants," Langkilde said.

Once the lizards reached adulthood – about a year – scientists evaluated the immune function of animals by measuring the ability of their blood plasma to retain foreign protein in suspension.

"We found that the offspring of lizards from highly stressed environments had suppressed immune function, while the offspring of lizards from under stressed environments had a stronger immune system when they were exposed to hormones. important for stress during their lifetime, "said McCormick. "This change is probably adaptive because a stronger immune response to stress should also improve survival in the presence of frequent attacks of fire ants."

An article describing these results appears online as a manuscript accepted January 18 in the Journal of Experimental Biology.

"This work poses several interesting questions," said Langkilde. "In a stressful situation, animals often divert their energy to essential functions, such as fleeing a predator, and moving away from less immediately critical functions, such as immune function, growth, or reproduction. In the short term, but can be expensive in case of stress.If the lizards of sites invaded by fire ants do not suffer from a compromised immune system, what are they trading? do they suffer from lower growth or repressed reproductive system, on the contrary, when they are exposed to very stressful environments? we intend to investigate. "

McCormick noted that understanding how species respond to stress can help manage them.

"In this changing world, animals can be confronted more often with stressful situations, in some cases due to new types of stressors such as human interactions or invasive species," he said. she said. "It is imperative to understand how species react to stress and, if this response varies from one population to another, in order to better allocate resources in order to mitigate the negative effects."