Amazing stuff!
"The brain ... is shielded from much of the body by the blood-brain barrier ... And historically, many scientists believed that separation extended to the immune system as well: The brain has its own specialized immune cells called microglia, but immune cells present in the rest of the body were long thought to steer clear of the brain unless there was a disease or other problem requiring their presence.
Now, a team of scientists ... has shown that immune cells known as T cells reside in the healthy brains of mice and humans, trafficked there from the gut and fat. This is the first time T cells have been shown to inhabit the brain under normal, non-diseased conditions. ...
The presence of T cells in the healthy brain and evidence that they travel between the brain and other parts of the body upend the field’s dogma about the role of T cells in the brain, the study authors say. Pathologists have seen T cells in the brain before, but it was assumed they were there responding to current or previous infections. ..."
From the abstract:
"Specialized immune cells that reside in tissues orchestrate diverse biological functions by communicating with parenchymal cells. The contribution of the innate immune compartment in the meninges and the central nervous system (CNS) is well-characterized; however, whether cells of the adaptive immune system reside in the brain and are involved in maintaining homeostasis is unclear.
Here we show that the subfornical organ (SFO) of the brain is a nucleus for parenchymal αβ T cells in the steady-state brain in both mice and humans.
Using unbiased transcriptomics, we show that these extravascular T cells in the brain are distinct from meningeal T cells: they secrete IFNγ robustly and express tissue-residence proteins such as CXCR6, which are required for their retention in the brain and for normal adaptive behaviour.
These T cells are primed in the periphery by the microbiome, and traffic from the white adipose and gastrointestinal tissues to the brain. Once established, their numbers can be modulated by alterations to either the gut microbiota or the composition of adipose tissue.
In summary, we find that CD4 T cells reside in the brain at steady state and are anatomically concentrated in the SFO in mice and humans; that they are transcriptionally and functionally distinct from meningeal T cells; and that they secrete IFNγ to maintain CNS homeostasis through homeostatic fat–brain and gut–brain axes."
No comments:
Post a Comment