If you're allergic to peanuts, milk or strawberries, you often blame your immune system, but when we can eat a wide variety of foods without any problems, few people realize that it's also because our immune system is working well.
The reason the body is able to accept chicken, beef or tomatoes - things that are foreign and can be perceived as threats - is thanks to an immune mechanism called "oral tolerance".
Although this mechanism plays a vital role, the exact way it works has remained a mystery for many years.
A study by Dr. Ranit Kedmi and his team at the Systems Immunology Department of the Weizmann Institute of Science (Israel), recently published in the journal Nature, has clarified the long-standing paradox and for the first time clearly identified the cellular network that coordinates the mechanism of food tolerance.
Food tolerance begins to develop in the fetus, when the immature immune system is exposed to food molecules through the mother.
This mechanism continues to develop during breastfeeding, when babies start eating solid foods, and through interactions with beneficial gut bacteria that produce allergenic molecules that the immune system learns to ignore.
For many years, scientists have believed that dendritic cells (DCs) are central to the regulation of food tolerance.
According to the discovery of Professor Ralph Steinman - Nobel Prize winner in Medicine in 2011, DC is known for its role in detecting and presenting pathogens to the immune system. The traditional view is that when DC encounters food, it will "order" not to attack.
However, in animal knockout trials of the suspected DC group, food tolerance still occurred, which has caused confusion among researchers.
Dr. Kedmi suspected the real culprit was a rare cell type she had discovered in her postdoctoral research: ROR-gamma-t (RORγt) cells of unknown origin. That suspicion proved correct.
New research by Dr. Kedmi and graduate student Anna Rudnitsky shows that it is RORγt cells, not DCs, that initiate tolerance.
When scientists removed the ability of these cells to present food molecules to the immune system in mice, they quickly developed food allergies.
Dr. Kedmi and his team continued to unravel the entire mechanism of tolerance. By selectively genetic manipulating and eliminating individual cell types in mice, combining advanced imaging technology and genomic tools, they identified a network of four cell types that work together to prevent the immune system from reacting to food.
This network starts with RORγt, then signals are passed through two other intermediary cell types before inhibiting a fourth cell type – CD8 immune cells, which are responsible for killing infected cells and triggering inflammation when a threat is detected.
One question that arises is if there are bacteria carrying proteins similar to food, will the immune system ignore them?
Scientists tested this by exposing mice to bacteria carrying food-like proteins. The results were surprising: The immune system paused its tolerance program, mobilizing CD8 to attack the pathogen. When the bacteria were killed, the tolerance mechanism was restarted.
The discovery of this cellular network helps explain why tolerance mechanisms fail, as in celiac disease (an intolerance to gluten - various proteins found in wheat and other grains), when CD8 attacks the intestinal lining, mistaking gluten for danger.
Understanding the break points in the tolerance network may open new treatment directions for food allergies and related disorders./.
Source: https://www.vietnamplus.vn/giai-ma-co-che-mien-dich-giup-con-nguoi-an-uong-khong-bi-di-ung-post1043249.vnp
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