Researchers at the University of Virginia School of Medicine have determined that the immune system directly affects, and even controls, social behaviour, such as the desire to interact with others.

The startling discovery raises fundamental questions about human choices.

The UVA researchers have shown that a specific immune molecule, interferon gamma, seems to be critical for social behaviour and that a variety of creatures, such as flies, zebrafish, mice and rats, activate interferon gamma responses when they are social. Normally, this molecule is produced by the immune system in response to bacteria, viruses or parasites.

Even problems like autism and schizophrenia could be caused by a block of this single type of immune molecule. A malfunctioning immune system may be responsible for social deficits in numerous neurological and psychiatric disorders.