AsianScientist (Feb. 5, 2016) – Scientists in South Korea have recently uncovered one of the key mechanisms that triggers immune tolerance to dietary antigens in the small intestines. Their work was published in Science.
Our immune system evolved to attack foreign materials entering our body. Food is technically foreign, but it is somehow tolerated by the immune system so that our body can absorb the nutrients. The immune system has built-in tolerance mechanisms that harness itself from responding to benign foreign antigens beneficial to our system, like food.
When such tolerance fails, we suffer from an overt immune reaction, such as food allergies, which can be severe enough to be fatal. Despite the increasing incidence and severity of food allergies, the details on how immune tolerance to dietary antigens is normally established remain largely unknown.
A key mechanism used by our body to induce immune tolerance is by induction of regulatory T (Treg) cells, a subset of white blood cell that suppresses other T cells. In the gut, a special subset of Treg cells called peripheral Treg (pTreg) cells exists in both the small and large intestine. Previous research showed that pTreg cells are created in the large intestine in response to the normal commensal intestinal bacteria, and which play a vital role in our health.
pTreg cells were also believed to exist in the small intestine to inform the immune system on which food antigens can enter our body. The research team has now discovered that a normal diet does indeed induce the creation of the pTreg cells in the small intestine.
Through a painstaking process, the team from the Academy of Immunology and Microbiology within the Institute for Basic Science in South Korea bred a special type of mice, dubbed “antigen-free” mice, which are completely devoid of any microorganisms, from germ-free parents. Like their parents, antigen-free mice are also germ-free, but they were also fed an ultra-refined “elemental” diet comprised of basic building blocks of life that keeps them alive and healthy, but is free of antigens (macromolecules) that can activate the immune system.
The result was that like germ-free mice, the antigen-free mice were depleted of pTreg cells in their colon, but what was new and exciting was that they also lacked pTreg cells in their small intestines. Hence, it became clear that normal dietary antigens were responsible for signaling pTreg cells to be generated at this site.
While this study didn’t focus directly on food hypersensitivity treatments, the antigen-free mice provided a better understanding of the processes involved in food allergies. This work brings us one step closer to understanding how the body’s immune response works and what we can do to control it.
“I believe that dietary antigens might also affect autoimmune diseases in other organs,” said study author Professor Charles D. Surh, implying that their work may have applications in other areas of biological research as well.
The article can be found at: Kwang et al. (2016) Dietary Antigens Limit Mucosal Immunity by Inducing Regulatory T cells in the Small Intestine.
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Source: Institute for Basic Science.
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