Study identifies possible connection to autism development

In recent years, science has increasingly uncovered how deeply our gut affects our entire body — not just digestion, but mental health, immunity, and even how we respond to stress. The human microbiome, made up of trillions of bacteria living inside our intestines, has become one of the most important frontiers in medical research. Now, a new study suggests it may also play a role in autism.

Published in The Journal of Immunology, the study sheds light on how a mother’s gut bacteria during pregnancy could influence the neurological development of her child. The research, conducted by scientists at the University of Virginia School of Medicine, centers on a molecule called interleukin-17a (IL-17a) — an immune system protein previously known for its role in inflammatory diseases like psoriasis, rheumatoid arthritis, and multiple sclerosis.

The World Health Organization defines autism spectrum disorder (ASD) as a group of developmental conditions that affect communication, social interaction, and behavior. Symptoms and cognitive abilities vary widely between individuals, but many people with autism also experience related conditions such as epilepsy, anxiety, depression, and ADHD. Scientists have long tried to understand what factors — genetic, environmental, and biological — may influence its development.

According to the study’s lead researcher, Dr. John Lukens, the microbiome appears to be a crucial piece of that puzzle. “The microbiome can shape the developing brain in multiple ways,” Lukens explained in a statement. “It’s vital for calibrating how the offspring’s immune system responds to infection, injury, and stress.”

To explore this connection, Lukens and his team conducted a series of controlled experiments using mice. They divided the animals into two groups: one had gut bacteria known to trigger strong inflammatory responses through IL-17a, while the control group did not. Both groups were then monitored for changes in brain development and behavior.

When researchers suppressed IL-17a activity during pregnancy, both groups of offspring displayed typical, healthy behavior. But when they allowed the molecule to act naturally, the offspring of the first group began to show behaviors that closely resembled symptoms seen in autism — repetitive actions, reduced social engagement, and unusual communication patterns.

To confirm whether gut bacteria were truly responsible, the scientists performed fecal transplants. They transferred fecal matter — and with it, the microbiota — from the first group of mice to the second group. Soon after, even the control mice began to show similar autism-like behaviors.

The findings suggest a strong causal link between a mother’s gut microbiota, her immune response during pregnancy, and potential effects on the developing brain of her offspring. “The results indicate that the mother’s microbiome, not the child’s, may have a greater influence on autism risk,” Lukens said.

IL-17a, the molecule at the heart of this research, is part of a larger family of proteins called cytokines. These signaling molecules play a key role in immune regulation — rallying the body’s defenses during infection and controlling inflammation. However, when cytokines like IL-17a are overactive, they can trigger excessive inflammation. In the case of pregnancy, this inflammation could interfere with fetal brain development.

While the results are based on animal models, the implications for humans are significant. Lukens believes this research could open the door to preventive strategies that focus on maternal health. “In terms of translating our work to humans,” he explained, “the next big step would be identifying specific features of the microbiome in pregnant mothers that correlate with autism risk. Once we understand that, we can begin exploring ways to modulate the microbiome safely.”

That last word — safely — is crucial. Blocking IL-17a may seem like an obvious solution, but Lukens cautions that interfering with the immune system during pregnancy could carry major risks. “If you think about it,” he said, “pregnancy itself is a delicate immune process. The mother’s body has to tolerate what is, essentially, foreign tissue — the developing baby. Maintaining that balance requires precise immune regulation, so most experts are reluctant to manipulate it.”

The goal, then, isn’t necessarily to eliminate IL-17a but to better understand the conditions that cause it to become overactive. This could mean identifying dietary, environmental, or microbial factors that shape the mother’s immune response. “IL-17a is just one small piece of a much bigger picture,” Lukens noted. “We still have a long way to go.”

The study builds on a growing body of evidence linking gut health to neurological and psychiatric conditions. Previous research has already associated imbalances in gut bacteria with anxiety, depression, and neuroinflammation. The so-called “gut-brain axis” — the constant biochemical communication between the digestive system and the central nervous system — is now considered one of the key systems influencing mood, cognition, and even behavior.

What makes this new study stand out is its focus on the maternal microbiome. If confirmed in humans, the findings could transform how doctors approach prenatal care. Diet, probiotics, antibiotic use, and even environmental exposures could all play a role in shaping the microbiome — and by extension, the developing brain.

Still, experts caution that this research is in its early stages. While mice share many biological pathways with humans, animal studies can’t always be directly applied to people. “It’s too soon to say that modifying a mother’s gut flora can prevent autism,” Lukens emphasized. “But it does provide a powerful foundation for future research.”

For now, the study serves as a reminder of how interconnected our systems truly are. The health of the gut influences far more than digestion — it shapes our immune defenses, our stress responses, and perhaps even the minds of the next generation.

If future research confirms these findings in humans, prenatal care might one day include microbiome monitoring alongside traditional screenings. Until then, maintaining a healthy gut — through a balanced diet, limited antibiotic use, and good lifestyle habits — remains a safe and beneficial step for everyone, especially expecting mothers.

As Lukens put it, “We’re learning that the story of brain development doesn’t begin and end in the brain itself. It starts in the gut — in a community of microbes that’s been evolving with us for millions of years.”

The link between the microbiome and autism is far from settled, but one thing is clear: the microbes inside us may be influencing our children in ways science is only just beginning to understand.