cells within the lining of the brain control anxiety-like behaviors in mice, researchers report today (September 14) in Nature Immunology. The findings increase mounting experimental evidence that these immune cells are involved in additional than fighting infection and should even contribute to cognitive functions. Commensal bacteria within the gut influence those T cells and should also shape the animals’ behavior, the scientists’ experiments show.
“I think the most important , most vital finding is that these T cells are releasing a signaling molecule, not in response to any quite infection or threat, to form sure that mice aren’t taking unnecessary risk,” says study coauthor Kalil Alves de Lima, an immunologist at Washington University in St. Louis (WUSTL).
In the study, Alves de Lima and his colleagues performed an in depth investigation of gamma delta T cells. These immune cells reside in tissues throughout the body, including the dura , the tough, outermost layer of the meninges. Called the “skin of the brain,” by Alves de Lima et al. , the meninges may be a set of three spongy membranes that line the skull and medulla spinalis and separate nervous tissue from the remainder of the body.
Alves de Lima discovered gamma delta T cells within the meninges while probing mice’s dura for helper and killer T cells. Curious to understand if humans harbored similar T cells in their meninges, Alves de Lima and his colleagues analyzed the dura of individuals who’d recently died; they too had gamma delta T cells there. The team then continued to review the meningeal gamma delta T cells in mice, and using flow cytometry, showed the cells were producing IL-17.
Diving into the literature, Alves de Lima found past studies probing the proinflammatory cytokine’s role in fighting infection, also as its contribution to autoimmune disorders, like atrophic arthritis , lupus, and MS . Until recently, though, there had not been many studies exploring the cytokine’s effect on behavior and cognition. A 2016 study showed that mouse pups born to mothers injected with an epidemic or synthetic double-stranded RNA to spur an immune reaction during pregnancy have changes in their brain architecture and exhibit autismlike behaviors. If the mouse moms lacked IL-17a, the pups showed no brain or behavioral changes. additionally , pups deficient within the IL-17a receptor also didn’t have brain or behavioral changes. A 2017 study in C. elegans also showed that the cytokine shaped the worms’ neuronal response to high levels of oxygen.
All of those experiments suggested that IL-17 played a task in something quite microbial defense, says Dan Littman, an immunologist at ny University Grossman School of drugs . He coauthored the study on autismlike behaviors in mice but wasn’t involved within the new work.
Last year, another team of researchers showed that gamma delta T cells within the meninges of healthy mice release IL-17a, which the cytokine influences the animals’ ability to form short-term memories.