The reason our 1.4kg brain doesn’t seem so heavy is because it floats in a reservoir of cerebrospinal fluid (CSF) that flows in and around the brain and spinal cord.
This liquid barrier between the brain and skull protects against head injury and nourishes the brain.
But cerebrospinal fluid has another important, albeit unknown, function: it also provides immune protection to the brain. However, this function is not well understood.
Research into cerebrospinal fluid in Northwestern Medicine has revealed its role in cognitive impairments such as Alzheimer’s disease.
Study lead author David Gate, assistant professor of neuroscience at Northwestern University’s Feinberg School of Medicine, said the discovery provides new evidence for the process of neurodegeneration.
A study started in the journal Cell found that the immune system in the cerebrospinal fluid deteriorates with age.
The researchers also found that the immune systems of people with cognitive impairments, such as those with Alzheimer’s disease, are radically different from those of healthy people.
“We now have a profile of the immune system in the brain during healthy aging and neurodegeneration. This immune reservoir could be used to treat encephalitis or as a diagnostic tool to determine the level of encephalitis in people with dementia,” Gate said.
“We are conducting a comprehensive analysis of this important immune reservoir for healthy and diseased brains,” he explained.
To analyze the cerebrospinal fluid, Gate’s team at Northwestern University used a sophisticated technique called single-cell RNA sequencing. They profiled 59 CSF immune systems of different ages by taking cerebrospinal fluid from participants’ spines and isolating their immune cells.
The first part of the study examined the cerebrospinal fluid of 45 healthy people aged 54 to 83 years.
The second part of the study compared these results in a group of healthy people with cerebrospinal fluid (CSF) in 14 adults with cognitive impairment, as determined by their poor performance on memory tests.
The team observed genetic changes in immune cells in the cerebrospinal fluid of healthy older people that cause the cells to become more active and inflammatory with age.
The scientists explained that inflammatory T cells in the cognitive impairment group replicated and spilled into the cerebrospinal fluid and brain as if they were following a radio signal.
The scientists found that cells have an excess of the cellular receptor CXCR6, which acts as an antenna. And this receptor receives a signal – CXCL16 – from the degenerating microglial cells of the brain to enter the brain.
“Perhaps the degenerating brain activates these cells and causes them to reproduce themselves and flow into the brain. They don’t belong there, and we’re trying to understand if they contribute to brain damage,” Gate said.
He continued: “The future goal is to block this radio signal or prevent the antenna from receiving this signal from the brain. And we want to know what happens when these immune cells can’t get to the brain with neurodegeneration.”
Gate’s lab will continue to study the role of these immune cells in brain diseases such as Alzheimer’s. The team also plans to tackle other diseases, such as amyotrophic lateral sclerosis (ALS).
Source: Medical Express