Researchers at the University of Virginia School of Medicine claim that the immune system directly affects or controls a part of one’s personality. Although more studies are still required, the research team suggests that a malfunctioning immune system plays a role in social deficits observed in some neurological and psychiatric disorders.

The study now available in the journal Nature shows the direct link between the brain and the immune system. Previously, scientists believed that the brain is somehow protected from immune problems due to its lack of direct connection with the immune system.

“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 a sign of pathology. 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,” says Jonathan Kipnis, chair of UVA’s Department of Neuroscience. “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.”

The researchers observed that the interferon gamma, normally produced by the immune system to fight parasites, bacteria and viruses, gets activated when animals like flies, zebrafish, mice and rats have social interaction, showing that this immune molecule is also important for social behavior. When this molecule was blocked, the mice that used to be hyperactive suddenly became less social. Restoring it returned the mice to their normal behavior.

The findings could have implications toward improving treatments used for patients with neurological problems such as autism-spectrum disorders and schizophrenia. However, the researchers believe that simply utilizing this one molecule won’t automatically result to a cure as the mechanism for this is likely to be complicated and requires further investigations.