For the first time, scientists have captured images of immune cells known as microglia eating brain cell synapses.
Although that sounds like the description of some terrifying autoimmune disease, the process – long predicted, and now confirmed – is thought to be wholly beneficial.
Microglia comprise about one tenth of the cells in the brain. They are similar in many ways to macrophages that attack infected, damaged or dead cells throughout the rest of the body and, indeed, function as the brain’s first line of defence against microbial or viral threats.
However, scientists have long suspected they perform a second, equally important function – nibbling away connections between brain cells, known as synapses, when they have become redundant or dysfunctional.
Now, at last, a team of researchers from the European Molecular Biology Laboratory in Hamburg, Germany, and Rome, Italy, have succeeded capturing microglia eating a synapse on film.
To do so, the team, led by Laetitia Weinhard, used a combination of correlative light and electron microscopy (CLEM) and light-sheet fluorescence microscopy to drill deep inside a mouse brain.
In recording the microglia in action, the scientists realised that the immune cells did not engage in a one-sided attack on synapses. Instead, both sides of the interaction engaged in a weirdly beautiful dance.
As the microglia approached, the synapses extended thin projections known as filopodia towards them.
“As we were trying to see how microglia eliminate synapses, we realised that microglia actually induce their growth most of the time,” Weinhard explains.
Andrew Masterson is a former editor of Cosmos.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.