Immune cells patrol the gut to ensure that harmful microbes hidden in the food we eat don’t sneak into the body. Cells that are capable of triggering inflammation are balanced by cells that promote tolerance, protecting the body without damaging sensitive tissues. When the balance tilts too far toward inflammation, inflammatory bowel disease can result.
Now, researchers at Washington University School of Medicine in St. Louis have found that a kind of tolerance-promoting immune cell appears in mice that carry a specific bacterium in their guts. Further, the bacterium needs tryptophan—one of the building blocks of proteins—to trigger the cells’ appearance.
“We established a link between one bacterial species—Lactobacillus reuteri—that is a normal part of the gut microbiome, and the development of a population of cells that promote tolerance,” said Marco Colonna, MD, the Robert Rock Belliveau MD Professor of Pathology and the study’s senior author. “The more tryptophan the mice had in their diet, the more of these immune cells they had.”
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