Study finds impaired immune cell function may affect brain development in autism.
Autism spectrum disorder affects how a person communicates, behaves, and interacts with others. It often involves repeated actions or intense focus on certain topics. Scientists have long tried to figure out what’s happening in the brain to cause these patterns. One area they’ve looked at is how the brain forms and trims connections between nerve cells. These connections, called synapses, are where brain cells talk to each other. In people with autism, studies have found too many of these synaptic connections, which might interfere with how the brain works. Normally, as a child grows, the brain removes extra or weak connections in a process called pruning. This allows the brain to work more efficiently. Cells called microglia, which act as the brain’s immune system, help with this cleanup job. They trim away unneeded synapses, like gardeners trimming overgrown branches. This process is especially active in early life and teenage years, when the brain is developing quickly.
But it’s hard to study microglia directly in people, especially in those with autism. Scientists can’t just go in and observe these cells in action in a living human brain. So researchers at Fujita Health University in Japan found a way to get around this. They used immune cells from the blood, called macrophages, which can be made to act in a way that’s similar to microglia. They turned these macrophages into two types using lab techniques—one type that responds more aggressively to problems and another that helps repair and regulate.
To see how well these lab-grown cells could clean up brain connections, the team added pieces of synapses, called synaptosomes, which were made from stem cells. These synaptosomes mimic the debris that would need to be cleared in the brain. When the macrophages came from people without autism, the ones designed to help repair (called M-CSF macrophages) did a better job clearing the synaptosomes. But when the cells came from people with autism, those same M-CSF macrophages didn’t perform as well. They showed a poor response when it came to cleaning up the synaptic material.
The researchers found that this difference in performance might be linked to a specific gene, CD209. This gene seems to play a role in helping the cells recognize and engulf the synaptic fragments. In people with autism, this gene was not as active, which may explain the poor cleanup response.
This discovery suggests that the problems seen in autism may not just be about brain wiring itself but could also involve how immune cells clean up the extra wiring. If microglia in the brain also show this same problem, it could explain why people with autism end up with too many synaptic connections. Those extra connections could confuse the brain’s messaging system and make it harder to filter and respond to information.
This kind of research is still new, but it’s an important step in figuring out why autism develops the way it does. Earlier studies mostly looked at the number of synapses or changes in brain activity after death. This one shows that even cells taken from the blood can show differences that might relate to what’s happening in the brain. It opens up new ideas for future treatments.
If future research finds the same kind of response in actual brain microglia, scientists might be able to develop treatments that help these cells work better. That could one day lead to therapies that support more balanced brain development and improve how people with autism think, feel, and interact.
For now, this study adds a new piece to the puzzle of autism. It shows that the body’s cleanup crew may be struggling to do its job, leaving behind too much clutter in the brain. And that clutter may be part of what makes social interaction and learning more difficult for people on the spectrum.
Sources:
Study links impaired synaptic pruning to autism
Impaired synaptosome phagocytosis in macrophages of individuals with autism spectrum disorder
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