Immune system can affect social behaviour: study

In a startling discovery, scientists have found that immune system can directly affect, and even change, social behaviour, a finding that may have great implications for neurological diseases such as autism-spectrum disorders and schizophrenia.
"Our findings contribute to a deeper understanding of social dysfunction in neurological disorders, such as autism and schizophrenia, and may open new avenues for therapeutic approaches," said Vladimir Litvak, assistant professor at University of Massachusetts Medical School (UMMS).
Litvak and Yang Xu, a PhD student at UMMS, developed and employed a novel systems-biology approach to study the complex dialogue between immune signalling and brain function in health and disease.

"Using this approach, we predicated an unexpected role for interferon gamma (IFN-gamma), an important cytokine secreted by T lymphocytes, in promoting social brain functions," Litvak said.
Using the new approach, Xu defined canonical immune signalling signatures and analysed for their presence in thousands of publicly available brain transcriptome data-sets.
These studies uncovered a hidden connection between T-cell mediated immune signalling and social brain function.

Researchers found that various organisms, including rodents, fish and flies, elevate IFN-gamma signalling in social contexts.
These findings suggest that the IFN-gamma signalling pathway may mediate a co-evolutionary link between social behaviour and an efficient anti-pathogen response that might be critical for herd immunity.

Jonathan Kipnis, of the University of Virginia School of Medicine showed that blocking IFN-gamma in mice made mouse brains become hyperactive and caused atypical social behaviour.
Restoring of IFN-gamma-signalling in the brain normalised brain activity and social behaviour.
"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," said Kipnis.
"And now, not only are we showing that they are closely interacting, but some of our behaviour traits might have evolved because of our immune response to pathogens," said Kipnis.
The researchers note that a malfunctioning immune system may be responsible for "social deficits in numerous neurological and psychiatric disorders."

However, exactly what this might mean for autism and other specific conditions requires further research.
The study was published in the journal Nature.