More and more, we are discovering that the mind and the body are not separate. The brain is not just an ivory tower that sends orders from on high to a body that just does what it’s told. The body talks to the brain, too. Indeed, a group of scientists recently discovered a two-way connection between the brain and the immune system, one that could have far-reaching implications.
For the longest time, scientists thought that the brain was totally separate from the body’s immune system—recent work has shown that’s not so. In the membranes that cover the brain and spinal cord, there are lymphatic vessels that can drain fluid and immune cells from the cerebrospinal fluid into the deep cervical lymph nodes, which are located in the neck. Researchers identified these vessels first in mice, then found a “potentially similar structure” in humans.
That was in 2015. Now, a new study has shown that the immune system’s connections with the central nervous system may actually affect how animals behave socially. The key is a molecule called interferon-gamma. T-cells, a type of white blood cell, in those vessels emit interferon-gamma (let’s just call it I-G, not to be confused with Instagram) into the brain. Once there, it inhibits neurons in the prefrontal cortex. This is normal—without I-G, that region can become overactive. And researchers have found that in mice, when the prefrontal cortex becomes overactive, they get asocial.