Infections and Autism

Our immune system is as complex as they come. And it needs to be to protect us from all the pathogens and various microbes trying to invade our bodies. But for all the excellent work it does, it is still not perfect. Every once in a while, something passes through. Unfortunately, most of the time it is something dangerous or deadly. Cancer cells are the most common thing that passes through our immune systems defense mechanisms. On top of that, our system can also harm us by going into overdrive. They can overproduce certain compounds which can then damage the body’s healthy cells.

And one of the most dangerous times our immune system can cause chaos is during pregnancy. If anything is even remotely wrong during this period, it might have negative implications for the developing fetus. A particular immune reaction may also have the ability to increase the risk of the fetus developing neurodevelopmental disorders like autism. This is a process known as maternal immune activation or MIA for short.

The issue is that scientists were unable to determine the mechanism behind this. How could an immune response be responsible for the increase of risk for contracting a neurodevelopmental disorder? Two mice studies were conducted to determine this. The scientists noticed that a certain bacterium in the mouse gut kicks the immune system into action and it produces inflammatory cells which then force the somatosensory cortex to show signs similar to the one which causes autism or another similar disorder in humans.

Thanks to this, scientists finally had something to go off of when looking into potential mechanisms which can trigger the development of autism. But as with any study conducted on mice, there is still much that needs to be tested to determine how this affects humans. The physiology of mice is similar to the one in humans, but they are in no way completely compatible.

A previous study has already shown that the presence of interleukin 17a in mice can cause them to pass on disorders similar to autism to their young. The problem was that the scientists were unable to determine how this mechanism works. The scientists did find microbes in the gut that pushed the immune system to create more interleukin 17a, though. What was interesting was that mice that did not have interleukin 17a in their system or mice that were administered antibiotics did not show signs of MIA.

Using something called optogenetics – which is the process of using light signals to alter proteins – the team of scientists was able to trigger behaviors in mice that simulate the ones during MIA by activating a specific region in the brain. In mice that had MIA, inhibiting certain neural activities stopped behaviors that caused the development of autism.

Because MIA is not something you might contract from a common cold, this information is of great value to pregnant women. This kind of response is triggered only during severe viral infections. Also, the diagnosis of these kinds of disorders is much more common during the late first or the second trimester. But there is still a chance that all this is more down to a genetic predisposition than to the effects of MIA.

Environmental effects might also have a significant role in all of this. There is a chance that a combination of environmental effects as well as other varying factors might be needed for a fetus to develop autism-like ailments. Still, these studies show that there is a direct connection between gut bacteria, the immune system, and brain development. Now it is up to the scientists to find out how they can best counter the bacteria that triggers these immune system responses.


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