Your Immune System Can Influence Your Social Life, Here's How

It's general knowledge that the immune system defends the body against harmful pathogens, but it appears that it has another, quite unexpected function - influencing a person's social behavior. This recent finding adds to a growing body of research on the ways in which the immune system shapes human behaviors and mental processes.

A study in Nature by a joint team of researchers from the University of Virginia School of Medicine and the University of Massachusetts Medical School presents evidence that the immune system can produce what one might call a "social molecule" that promotes interactivity with others. This suggests that some cases of social dysfunctionality may be linked to problems in the immune system.

Until recently, most people have assumed that the brain and the immune system work in isolation from one another, but it is now know that this is not the case. As Genetic Engineering News (GEN) notes, "a team of scientists based at the University of Virginia Health System established just a year ago that meningeal vessels directly link the brain with the lymphatic system."

GEN reports co-lead author Jonathan Kipnis of UVA's Department of Neuroscience saying, "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... Part of our personality may actually be dictated by the immune system."

Research into the intriguing linkage between the immune system and the brain has previously turned up evidence suggesting that the immune system can inform spatial learning and memory formation. Kipnis and his team have been investigating its influence upon pro-social behavior.

Their research centered in on a cell-signaling molecule generated by T lymphocytes. Known as interferon gamma, it is a cytokine - a protein that "talks" to other cells to get them to perform certain actions.

The team examined the interferon gamma response in mice, finding evidence of a strong interaction between social behavior and cytokine-driven activity. They were able to demonstrate that inhibitory neurons release GABA in response to interferon gamma - which is generally an indication of more positive mood and less social anxiety.

In a meta-analysis, they also found that organisms as diverse as zebrafish, flies, mice and rats showed an interferon gamma response during pro-social interactions. Applying a genetic modification that blocked the "social molecule" in mice resulted in unnaturally hyperactive neuronal activity associated with less social behavior. This suggests that the immune system facilitates sociability, and when it malfunctions, there is a corresponding downswing in social personality.

The study results raise the possibility that defects of the immune system can bring about maladaptive social behaviors, which in severe cases may be classifiable as psychiatric disorders. The researchers are calling for further investigation, suggesting that this area of study may lead to a better understanding of conditions such as autism.