Nature: These immune cells are all over the brain, and their origin and function have just been discovered…

▎WuXi AppTec Content Team Editor The brain is often referred to as the commander of the whole body
.

To protect this vital organ from microbial infection or other toxic substances, the rich blood vessels form a barrier between the brain parenchyma and the blood
.

The blood-brain barrier, mainly composed of vascular cells, strictly filters the substances that enter the brain from the blood, thereby ensuring that the brain is in a relatively stable and safe environment
.

At the same time, the microglia stationed in the brain tissue, as innate immune cells, "monitor" the environment of the brain parenchyma, identify and phagocytose pathogens, etc.
, and build a line of defense to protect the brain
.

Image credit: 123RF And only recently has an important new member of the immune defenses that protect the brain become known
.

In a research paper recently published in the top academic journal "Nature", researchers from Kyushu University in Japan and the University of Freiburg in Germany (University of Freiburg, Germany) conducted a study of another type of innate immune cells throughout the brain, revealing for the first time.
Their formation process, as well as enhancing important functions such as the blood-brain barrier
.

The researchers pointed out that detailed analysis of these special immune cells is expected to elucidate the mechanism of brain development, as well as the pathogenesis and treatment of various brain diseases
.

The type of immune cells the study focused on, like microglia, are macrophages
.

However, unlike microglia, which are distributed in the brain parenchyma, these macrophages are located in the meninges and surrounding blood vessels that wrap the brain
.

Using cutting-edge single-cell analysis techniques, cell fate tracking, and cell-specific transgenic mouse models, the researchers labelled different types of brain macrophages and their progenitors to confirm these Specialized macrophages and microglia distributed in the meninges, blood vessels, etc.
share the same progenitor cells in the embryonic stage
.

▲Microscopic images show macrophages in different tissues in the mouse brain (Image source: Reference [2]; Credit: Medical Center—University of Freiburg / Dr.
Lukas Amann) However, although precursor cells are early in the brain were in place, but these specialized macrophages matured later than expected
.

The researchers confirmed the maturity of individual cells by examining their gene activity
.

"We found that these immune cells migrate from the meninges to the cerebral blood vessels shortly before birth, where they mature
.

This process is not completed until about a few weeks after birth ," said Professor Marco Prinz, co-corresponding author of the study
.

It's fragile to begin with, and I think that's part of the reason
.

" Further research revealed that the reason these special brain macrophages do not mature until after birth depend on vascular smooth muscle cells providing important signals
.

▲ Schematic diagram of the different developmental trajectories of perivascular macrophages (pvMΦ), meningeal macrophages (mMΦ) and microglia (Image source: Reference [1]) “In addition to the blood-brain barrier, these immune cells we studied also Controlling what gets from the blood to brain cells, they engulf pathogens and prevent excessive inflammation, and they are also involved in the development of cancer, Alzheimer's disease and multiple sclerosis,
"
added Professor Prinz
.

The researchers believe that as the understanding of these types of brain immune cells grows, there will also be new understandings to better understand the pathogenesis of these diseases, and opportunities to develop new cell-targeted therapies based on this
.

Reference: [1] Takahiro Masuda et al.
, Specification of CNS macrophage subsets occurs postnatally in defined niches.
(2022) Nature https://doi.
org/10.
1038/s41586-022-04596-2[2] New discoveries about the origin of the brain's immune system.
Retrieved Apr.
24, 2022 from https://medicalxpress.
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