Bile Acids Control Differentiation, Activity of Immune Cells that Play Key Role in IBD, Mouse Studies Find

Bile Acids Control Differentiation, Activity of Immune Cells that Play Key Role in IBD, Mouse Studies Find
Bile acids — acidic liquids produced by the liver and gallbladder to help the body digest food fats — promote the differentiation and activity of different types of immune cells that play a key role in bowel inflammation and in autoimmune disorders such as inflammatory bowel disease (IBD), according to data from two separate mouse studies. The two studies, both published in the journal Nature, also found that gut microbes — clusters of bacteria living in the intestine — seem to be responsible for converting bile acids into molecules that control the activity of immune signaling cascades. In the first study, "Bile acid metabolites control TH17 and Treg cell differentiation," researchers from Harvard Medical School (HMS) and their colleagues discovered specific metabolites of bile acids that are able to interact, activate, and promote the differentiation of two types of gut immune T-cells. These are the regulatory T-cells (Tregs) and a class of T-helper cells, called TH17. Tregs and TH17 are two different types of immune cells that are responsible for controlling and balancing immune and inflammatory responses in the gut. However, they do so in different ways.  TH17 are pro-inflammatory cells that promote inflammation to quell infections caused by harmful microbes. Meanwhile, Tregs are anti-inflammatory cells that are normally activated to curb tissue inflammation once the source of infection has been eliminated. When TH17 cells are overactive, like in the context of many autoimmune diseases, they trigger widespread tissue inflammation that can damage the intestine. In these experiments, the researchers exposed undifferentiated, or naïve, mouse T-cells to different bile acid metabolites. They found two derivatives of lithocholic acid (LCA) that ha
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