Defending the brain, with microglia

This post is also available in Dutch.

Just like the rest of the body, the brain needs well regulated protection. But who is responsible for this important job? And how can we relate brain diseases to these patrons of the brain?


Illustrated by Roselyne Chauvin

What are microglia?

The brain is mainly made up of two major groups of cells, the well known neurons and the glia-cells. The latter consists of three cell types, but the ones we’re particularly interested in are the microglia. Just like the macrophages eat and digest the bad particles in the body, microglia execute this function in the brain. These immune cells, that battle against bad particles (called pathogens), are very important in the development of diseases.

We’ve known about the existence of microglia for about a century, and shortly after researches speculated about microglia being the immune cells of the central nervous system. Still it wasn’t until 1988 researchers were able to proof their hypothesis that microglia have functions that resemble those of macrophages.

But are they macrophages? Researchers were able to measure a certain chemical which proved that microglia were able to perform phagocytosis, which is the eating and digestion of pathogens, and other similar functions. Further research showed significant differences between macrophages and microglia. They stated that microglia are rather cousins of macrophages than brothers.

Main function of microglia

Microglia can only be found in the central nervous system. Primarily these cells are in an inactive state, called the ramified state. This means they are resting because there is no suspicious action going on around them. Whenever the brain suffers some kind of damage the microglia will be activated and transform: they become more round and will act as some sort of macrophages for the brain.

New insights

Recent study have proven there are different compositions of the microglia population throughout the brain. They’ve been able to examine the different functions that microglia mainly practice in different brain areas. For example, microglia in one area of the brain reveal high defense-response, while microglia in yet another part seems more occupied with detecting pathogens.

The study also looked at the changes in microglia related to aging. The behaviour of the microglia changes over time, but not at the same rate in each brain area. In the cerebellum, which is related to movement execution, the microglia are very sensitive for aging. In the hippocampus, which is more involved in memory, the microglia age completely differently.

Application in new research

Now we know that microglia behave and age differently in the brain, loads of new research initiatives can be considered. Aging lies at the basis for many diseases. Diseases that are related to aging and have a different development in brain areas often come along with malfunctioning microglia, but what causes these malfunctions? Can this be linked to the difference in microglia population throughout the brain?

Research concerning Alzheimer’s disease, Multiple Sclerosis,… may benefit from these findings. Understanding the role of microglia in aging processes, provides lots of perspective for curing these diseases.

About the writer

This blog entry was written by Robin. Robin is a bachelor student in Biomedical Sciences at Radboud University. She broadened her knowledge about microglia during her observational mini-internship at Donders Institute.

Edited by Roselyne Chauvin

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