A molecule links the immune system to mental health

If we can harness a unique relationship, new mental health treatments could be found.

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The notion that the immune system exists only to protect the body from infection and disease is an idea increasingly outdated.

A study published in September supports a new way of thinking: Its findings suggest that the brain and the body likely share a symbiotic relationship.

Inverse is counting down the 20 stories redefining 'human' from 2020. This is number 17. See the full list here.

What was discovered — The researchers identified an immune molecule, IL-17, as a key tie between the two systems.

IL-17 is a pro-inflammatory cytokine, meaning it causes inflammation in the body in the event of an intruder. The researchers noticed that the tissues surrounding the brain were packed with the immune cells that make IL-17, called gamma-delta T cells.

When these cells were removed from mice, the animals acted largely the same in all the tests they were put through, save for one major difference — they exhibited more anxiety-like behavior. This finding suggests that the molecule might be potentially linked with anxiety in people.

One of the study’s authors, Jonathan Kipnis, a professor of neurology at Washington University, said these findings point to our brain and our immune system as being closely intertwined.

“Our behavior is very much dependent not only on the state of the brain but also on the state of the immune system,” Kipnis told Inverse.

“We all know how we feel when we are sick. This is a normal interaction between the two systems when the immune system signals the brain to ‘withdraw’ upon infection.”

Next, the researchers want to investigate how IL-17 impacts anxiety in humans. It could be that “the overstimulation of this pathway could be ultimately involved with anxiety and depression in humans,” Kalil Alves de Lima, the study’s first author and a research associate at Washington University, told Inverse.

Digging deeper into this connection could potentially lead to new treatments for mental disorders in the future, such as anxiety and depression.

Inverse is counting down the 20 stories redefining 'human' from 2020. This is number 17. Read the original story here.

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