Scientists have long theorised that the immune system has a more neurological connection than previously thought, and research has risen up to validate them. Recent studies, for example, have found that there is a physical connection between the immune system and the brain's blood supply, and now there seems to be a more psychological connection.
Now, researchers at the University of Virginia and the University of Massachusetts Medical School are suggesting the immune system directly affects social behaviour in certain creatures, such as mice, which can have profound implications for humans with autism-spectrum disorders and schizophrenia.
In a paper published in Nature this week, the researchers highlighted a specific immune molecule called interferon gamma, which is activated in various animals when they want to be social. When this molecule was genetically blocked in mice, their brains become hyperactive, specifically preventing the areas of the brain that govern social interaction.
As such, the scientists found the creatures were without access to the molecule interacted less other mice in their environment, despite the fact that mice are usually incredibly social creatures.
"It's like a little airport in small cities [suddenly] become major hubs and so there's a mess [of traffic congestion] in the air," said Jonathan Kipnis, chair of UVA's Department of Neuroscience and one of the authors of the study. "Same thing happens with the brain, so [the] brain cannot function properly."
Reintroducing the molecule back into the immune system calmed down the hyperactivity, therefore restoring typical social behaviours.
Additionally, the researchers prescribed a possible evolutionary cause for this occurrence: the relationship with people and pathogens, and the benefits of being social for a species to survive. When we interacted with others, it's suggested that our immune systems would respond so that we could protect ourselves from any diseases that could be spread.
"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," Kipnis added.
Of course, this theory has only been tested in mice, so there isn't a correlation yet in humans, or even evidence that this connection exists, but Kipnis and the other authors believe that this could have implications for people with social disorders.
Check out the researchers talking more about the study below: