Researchers have disclosed the nature of how T cells protect the brain against harmful viruses. The results of the study, which are published in Nature Communications, are important for investigating the role of the immune system in numerous brain disorders.

The immune system protects the body against infections and cancer. The so-called T cells play a key role in this process. When T cells do not work properly, an inflammation can develop in for example the brain. Until recently, little was known about the properties of these cells in healthy brains. "With this research, we have gained more knowledge about the location of T cells in the brain, how they look, what kind of inflammatory proteins (cytokines) they produce, and how they are controlled," says the researcher.

Authors show that human white matter-derived brain CD8+ T cells can be subsetted into CD103−CD69+ and CD103+CD69+ T cells both with a phenotypic and transcription factor profile consistent with TRM cells. Specifically, CD103 expression in brain CD8+ T cells correlates with reduced expression of differentiation markers, increased expression of tissue-homing chemokine receptors, intermediate and low expression of the transcription factors T-bet and eomes, increased expression of PD-1 and CTLA-4, and low expression of cytolytic enzymes with preserved polyfunctionality upon activation.

Brain CD4+ T cells also display TRM cell-associated markers but have low CD103 expression.

"If we understand the rules of the game, which T cells in the brain adhere to, then we can understand how T cells deviate from this in brain disorders. This can lead to advances in the understanding and treatment of diseases such as multiple sclerosis, but also in the treatment of tumors in the brain. "

https://www.nature.com/articles/s41467-018-07053-9

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