Immunity Affects Your Alertness and Anxiety Levels

Our bodies are turning out to be less machine like and instead much more intricately interrelated as researchers at Washington University School of Medicine uncover more connections between our immune system and our brain’s functions.  This should come as no surprise as everyone who has had the flu or other bad virus knows the mood change that comes along with the illness. It is not just because we are sick that we are in a bad mood.  The immune responses actually directly affect brain function through chemical reactions.  These researchers uncovered another mechanism by which this happens.

While the brain has a limited immune system residing within the actual nerve cell environmental, it appears that a cytokine call Interleukin 17 (IL-17) can diffuse into the brain from surrounding immune cells and trigger behavioral changes.  This cytokine has also been linked to autism and depression risk in humans.  The surrounding cells which produce IL-17 are called gamma-delta T cells. These cells produce an ongoing baseline of IL-17 which diffuses into the brain’s surrounding fluid.

To determine the effects of this cytokine on mouse behavior, they blocked the production of the cytokine.  The mice with lower levels were more likely to venture out into open areas of the test cages suggesting a lower level of anxiety about being in the “dangerous” open.

There is obviously much more research to be done to understand how varying levels of this cytokine might influence human health and behavior.  The researcher’s further experimentation with the effects of lipopolysaccharide on IL-17 production suggest possible links with our gut microbiome and brain function.  When they gave the mice LPS, a very inflammatory product of bacterial metabolism, the gamma-delta T cells produced more IL-17 in the mouse brains.  When they gave the mice antibiotics, the levels of IL-17 lowered suggesting that the mouse’s immune system could sense and response to varying levels of bacteria and inflammation and then affect behavior of the mice.

As research progresses, I believe we will see more and more connections like this between our microbial neighbors, our immune system, and various mental health conditions.  The impact of healthy nutrition on our gut microbiome will become more recognized as these mechanisms are uncovered.  Understanding this web of interconnected processes will be critical for healthy immunity for 2020 and beyond.

Original Article:

Kalil Alves de Lima, Justin Rustenhoven, Sandro Da Mesquita, Morgan Wall, Andrea Francesca Salvador, Igor Smirnov, Guilherme Martelossi Cebinelli, Tornike Mamuladze, Wendy Baker, Zach Papadopoulos, Maria Beatriz Lopes, William Sam Cao, Xinmin Simon Xie, Jasmin Herz, Jonathan Kipnis. Meningeal γδ T cells regulate anxiety-like behavior via IL-17a signaling in neurons. Nature Immunology, 2020; DOI: 10.1038/s41590-020-0776-4

Thanks to Science Daily:

Washington University School of Medicine. “Immune system affects mind and body, study indicates: Immune cells produce molecule that influences vigilance, alertness in mice.” ScienceDaily. ScienceDaily, 14 September 2020. <www.sciencedaily.com/releases/2020/09/200914131915.htm>.