Mouse models are clearly important in translational research, and we rely on pre-clinical mouse studies to determine whether treatments are safe enough for human testing. But despite our reliance on the humble mouse, clinical results don’t always match up with our expectations. A solution to boosting accuracy might lie with researchers investigating mice immune systems.

“In our new studies, we aimed to improve on the mouse model by exploring the impact that natural exposure to normal house microbes have on the immune response (1),” says Stephen Jameson, co-lead researcher and Professor in the Center for Immunology at the University of Minnesota.

The researchers, led by Jameson and David Masopust, tested the T-cell populations of lab mice, free-living barn mice, and pet-store mice and found that lab mice display an immune system closer to that of a newborn human, while the free-living and pet-store mice more closely resembled the immune systems of adult humans.

But were the immunological differences innate or environmental? To find out, the researchers co-habited lab mice with pet-store mice before re-testing the T-cell populations. After 15 days of mixing with the their less fastidious furry friends, the percentage of CD44 cytotoxic T cells increased in lab mice, bringing their immune systems closer to that of adult humans.

Though the results indicate that lab mice in “dirty” conditions may be better suited to pre-clinical studies, Jameson doesn’t believe the existing model should be completely replaced. “Valuable studies will continue to involve the current approach of maintaining mice in barrier facilities; for example, immunodeficient mice must be kept in lab conditions to survive,” he says, “but on the other hand, since our research showed that ‘dirty’ mice have many immunological features in common with adult humans, we propose that using these animals will be a much closer approximation to the response of the human immune system, with clear implications for testing drugs and other therapeutics for their impact on the immune response.”

Jameson also acknowledges that the new findings only scratch the surface of potential research directions with dirty mice, and has planned further detailed studies. “We will address three main areas with the new mouse model: immune response to cancer immunotherapy, the incidence of allergic and asthmatic disease, and the generation/control of autoimmune diseases,” says Jameson.