To confirm the evolutionary link between immunity and social behavior traits, the researchers analyzed the genomes of a range of rodent species, as well as zebrafish and fruit flies that had been used in previous lab experiments. Amazingly, they discovered that animals that had been housed in social enclosures had an upregulated IFN-γ gene, while animals kept in solitary confinement displayed a downregulation of this gene.
This suggests that these species are all genetically programmed to produce IFN-γ when they interact with others, regardless of whether or not they have been infected with a pathogen. As such, it seems likely that IFN-γ is highly involved with the activation of social behaviors, while simultaneously protecting against any infections that may result from these interactions.
Based on this finding, the study authors speculate that “immunity may also contribute to modulating neuronal circuits that are responsible for our everyday behaviors and personality.” Furthermore, they suggest that many social and personality deficits in humans may, in fact, be caused by faulty immune systems, and hope that this discovery one day leads to new treatments for conditions such as autism and other similar disorders.