Interleukin 17

Interleukin 17A is a pro-inflammatory cytokine.

In autism-spectrum disorder
Recent research has led some to believe that IL-17 may have a significant role in the development and persistence of autism through its inflammatory effects on the brain. Inspired by the observation that fever often temporarily reduces the behavioral deficits in autistic children, researchers discovered it may be the production of IL-17 during the fever state that causes these changes.

Though cytokines are immune-modulating agents, IL-17 was shown in one study to work like a neuro-modulator in mice with autism-like behavioral changes, having the paradoxical effects of increased risk of behavioral changes when exposed in-utero to maternal IL-17, but decreased behavioral abnormalities in adult mice. The mechanism by which IL-17 seemed to create these changes was by affecting the brain region S1DZ, part of the somatosensory cortex that is likely responsible for sensing where the body is in space.

In reference to IL-17's role in the brain, one researcher from the latter study said, “What’s fascinating about this communication is the immune system directly sends its messengers to the brain, where they work as if they’re brain molecules, to change how the circuits work and how the behaviors are shaped.” These findings may be significant to people with M.E. because they demonstrate the role of inflammation and immune-modulated cytokines on the central nervous system and behavior.

Further studies have demonstrated the importance of IL-17 production in response to gut bacteria in the modulation of autism as well, which may also hold clues for those who suspect their M.E. symptoms to be due to neuroinflammation and/or the result of an infection.