Life in the Wild Strengthens the Immune System

Living in a wild, demanding environment, where the resources are limited, could be better for the immune system than living in absolute comfort, concluded a new research, carried out at the University of Bristol.

The leader of the study was Professor Mark Viney, who, along with his colleagues, made a comparison between the immune systems of wild mice and that of mice bred in captivity.

The results were somehow predictable: wild mice had a better immune system, and also, by far, a more variable immune function.

It appears that mice have to choose the amount of resources, including energy and nutrients, to invest in several aspects of their life, like reproduction, competing for food and for mates, maintaining body condition and immune function.

The order of priorities is usually set by the different environments, like, for example, investing heavily in immune function to prolong healthy life (live long and safely), or taking daily risks just to favor reproduction (live fast and riskily).

These are extremes, of course, but the idea behind them is most important, and Professor Viney explained that “as a result of these different ‘choices’, we might expect wild animals to have very different immune responses from their captive cousins.

“Our findings suggest these wild mice are investing in immune responses to live long and safely, and doing so more than the captive mice.”

Wild mice have to find their own food in an often hostile environment, while mice bred in captivity have all food and lodging provided for them.

“We might be seeing an effect rather like that in the story of the Town Mouse and the Country Mouse where different environments provide different types of challenge to individual animals and cause them to adapt and respond differently,” said Professor Viney.

The next step for the researchers' team is to understand the reason why the immune responses are this varied, and to find out what influences the immune function of an individual animal.

The study is published today in Molecular Ecology.