A quarterly publication of the Autism Research Institute
Summer, 2016 | Number 3, Volume 30
A new study by researchers at the University of Virginia reports surprising evidence that the immune system directly affects social behavior.
“The brain and the adaptive immune system were thought to be isolated from each other, and any immune activity in the brain was perceived as sign of a pathology,” study coauthor Jonathan Kipnis says. “And now, not only are we showing that they are closely interacting, but some of our behavior traits might have evolved because of our immune response to pathogens. It’s crazy, but maybe we are just multicellular battlefields for two ancient forces: pathogens and the immune system. Part of our personality may actually be dictated by the immune system.”
Last year, the researchers discovered that meningeal vessels directly link the brain with the lymphatic system, disproving the accepted idea that the brain was “immune privileged” and did not have a direct connection to the immune system. Their new study indicates that in mice, one specific immune system molecule — interferon gamma — plays a crucial role in social behavior.
Normally, the immune system produces interferon gamma in response to infections. When the researchers blocked the molecule in mice, regions of the brain became hyperactive and the mice became less social.
The researchers note that social behavior is critical for the survival of a species, but social behavior also exposes the members of the species to infection. “So you need to be social,” lead author Anthony Filiano says, “but [when you are] you have a higher chance of spreading pathogens. The idea is that interferon gamma, in evolution, has been used as a more efficient way to boost social behavior while boosting an anti-pathogen response.”
The researchers say that anomalies of the immune system may be one cause of the social deficits in disorders such as autism and schizophrenia. While the researchers stress that interferon gamma is likely to be only one factor in these disorders, Kipnis says that their finding “has potentially very important clinical implications.”
“Unexpected role of interferon-γ in regulating neuronal connectivity and social behaviour,” Anthony J. Filiano, Yang Xu, Nicholas J. Tustison, Rachel L. Marsh, Wendy Baker, Igor Smirnov, Christopher C. Overall, Sachin P. Gadani, Stephen D. Turner, Zhiping Weng, Sayeda Najamussahar Peerzade, Hao Chen, Kevin S. Lee, Michael M. Scott, Mark P. Beenhakker, Vladimir Litvak, and Jonathan Kipnis, Nature, July 13, 2016 (online). Address: Jonathan Kipnis, Center for Brain Immunology and Glia, School of Medicine, University of Virginia, Charlottesville, Virginia 22908.
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“Shocking new role found for the immune system: controlling social interactions,” news release, UVA School of Medicine, July 13, 2016.
