How does the body know that a cookie is food and not a threat? Every time someone eats a meal or tastes a snack, the immune system faces an important choice.
The immune system can either accept the food or treat it like something dangerous. In most cases, the body makes the right choice and allows the food to pass safely through digestion. Scientists call this process oral tolerance.
A new study led by Stanford University scientists has helped explain how this process works. Researchers discovered tiny parts of food proteins that signal the immune system to stay calm.
This discovery helps explain how the body recognizes many foods as safe and could guide new treatments for food allergies.
Understanding the body’s decision
Food enters the body many times each day. Despite this constant exposure, the immune system usually avoids attacking food. Instead, the immune system learns to tolerate it.
The research team explored how the body makes the decision to maintain this balance, which keeps digestion smooth and prevents harmful reactions.
Dr. Jamie Blum, the study’s lead author, carried out the research at Stanford and later joined the Salk Institute.
The researchers discovered specific protein fragments in foods that communicate with immune cells. These fragments help immune cells understand that certain foods are harmless.
The role of regulatory T cells
The immune system contains many types of cells that work together to protect the body. One special group of cells helps prevent unnecessary immune attacks. These cells are called regulatory T cells.
Regulatory T cells act like peacekeepers. Instead of triggering inflammation, these cells calm the immune system. This calming action helps the body tolerate harmless substances such as food.
Scientists already knew that regulatory T cells play an important role in oral tolerance. However, researchers did not know which food proteins activate this response.
Understanding the body’s reaction to food
The Stanford team searched for answers by studying how regulatory T cells react to food proteins. The results helped reveal what signals guide the immune system toward tolerance instead of rejection.
“As someone interested in foundational science, there’s value in understanding a normal immune process along with pathology,” said Dr. Blum.
“Understanding how the immune system can normally see a protein as safe may lead to new therapies to promote tolerance in individuals with allergy.”
Why food allergies happen
Food allergies occur when the immune system mistakenly treats food as a threat. Instead of accepting the food, the immune system launches a defense reaction.
About six percent of children and up to four percent of adults experience food allergies. Common triggers include peanuts, eggs, soy, and other foods.
During an allergic reaction, the immune system identifies certain proteins in food as harmful. Antibodies recognize these proteins and activate immune cells such as mast cells and basophils. These cells release chemicals that cause inflammation and allergic symptoms.
Scientists have already identified many proteins that trigger allergies. However, much less was known about which proteins encourage tolerance.
Discovering the tolerance signals
To solve this mystery, researchers began with a simple approach. The team studied mice that ate a normal diet. Scientists then examined regulatory T cells to see which food proteins those cells recognized.
This investigation revealed three small protein fragments called epitopes. Each epitope came from a different plant food. One appeared in corn, another in wheat, and the third in soybean.
All three fragments came from seed proteins. Seed proteins exist in large amounts in many plant foods. The discovery suggests that the immune system often learns tolerance by recognizing these common plant proteins.
Corn produced the strongest response from regulatory T cells. This finding makes sense because corn rarely causes allergies. Soybean allergies are more common, so identifying a soybean epitope offers an exciting clue for future research.
The researchers also discovered something surprising. The receptor that recognizes the soybean protein fragment can also interact with sesame proteins.
This connection may explain why tolerance to one food sometimes leads to tolerance to another food.
Where these immune cells work
The study also explored where regulatory T cells perform their work. Experiments using mice and laboratory cell cultures helped answer this question.
The results showed that many regulatory T cells live in the gut. This location places the cells exactly where food enters the body.
The environment inside the gut also affects how these cells behave. In a healthy gut, regulatory T cells help maintain calm conditions with little inflammation. When inflammation appears, the cells act to reduce it and restore balance.
This flexible response allows the immune system to adjust based on what happens inside the digestive system.
A future without food allergies?
The discovery of these food epitopes opens new possibilities for treating allergies. Scientists already view regulatory T cells as a promising tool for future immunotherapies.
Researchers may eventually design regulatory T cells that recognize specific food proteins and promote tolerance. Such treatments could reduce allergic reactions or even prevent them.
“Diet is our most intimate interaction with our environment,” said Dr. Blum.
“Correctly recognizing foods as safe creates an anti-inflammatory environment to support nutrient acquisition and prevent allergy.”
“Our research advances scientific understanding of the major dietary allergens, and points us toward future therapeutic interventions that could redirect allergic and autoimmune states.”
Future research directions
Scientists now hope to apply this research to humans. The team has already created a special reagent that helps track these food proteins.
Other researchers can now use this tool to explore oral tolerance in greater detail.
Each meal may look simple, but the immune system performs an extraordinary task behind the scenes.
New discoveries bring science closer to understanding how the body peacefully accepts the foods that sustain life.
The study is published in the journal Science Immunology.
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