An international research team with Salzburg participation has now shown in the journal “Nature” that CD8 T cells apparently influence the brain of sick people. In the future, the new findings could also result in therapy and diagnostics.
CD8 T cells are part of the acquired immune system, that is, the part of the body’s own defense system that is continually developed over the course of life by dealing with pathogens of all kinds. When this cell subtype becomes active, the immune cells release molecules into their environment that trigger inflammation or initiate cell death. It is actually their job to act against cells infected with viruses or cancer cells.
The idea that the immune system can also play a role in the brain has only been pursued more intensively in science for around ten years. “The fact that it can even have a massive impact is becoming increasingly clear. You can see that the blood-brain barrier is not always 100% sealed. Especially in neurodegenerative diseases such as Alzheimer’s, it is sometimes open or somewhat more permeable. In addition, blood cells such as CD8 find T-cells find their way into the brain via the cerebral fluid, the so-called cerebrospinal fluid, “explained Salzburg neuroscientist Ludwig Aigner, who was involved in the publication, in an interview with APA.
The team led by Tony Wyss-Coray and David Gate from Stanford University (USA), which included Aigner and Michael Unger, another researcher from the Paracelsus Medical University in Salzburg, has now found that a subtype of these CD8 T cells in patients with Alzheimer’s or a precursor to the disease occurs more often. The long-established cooperation with the US team from Wyss-Coray found a new hanger after the Salzburg researchers noticed these cells in mouse brains some time ago, while the US colleagues in the blood and brain fluids of sick people regardless were found. The researchers first noticed the connection at a specialist conference. “This naturally gives our data much more value,” said Aigner.
“There is every indication that these cells appear to be activated outside the brain, that is, they are activated. When they arrive in the brain, they are ‘unlocked’ and given the ‘license to kill’,” said Aigner. They are apparently particularly active in the hippocampus, the region of the brain that is central to remembering. The trigger of Pfeifferer’s glandular fever, the Epstein-Barr virus, may also play a role in the process of rendering the CD8 T cells.
“We are interested in the question of what these cells actually do in the brain and whether they actually promote neuropathology,” said Aigner. Initial evidence suggests that they actually affect brain function. “It can be assumed that they destroy neurons there, but we don’t yet know,” said the scientist.
However, their presence could also help to better diagnose Alzheimer’s in combination with other factors in the future. If CD8 T cells actually turn out to be disease drivers, the course of their blockage could be influenced during therapy.
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