Sunday 22 August 2021

Simple compound to control complex gut microbes


Commensal bacteria can harm our health if they are out of control. Therefore, understanding the way the body regulates the balance of intestinal bacteria is important issue for staying healthy.


Immunoglobulin A (IgA) is the most abundant antibody produced in the human body, mostly secreted from the mucosal surfaces of the intestinal tract. IgA is thought to regulate the growth, colonization, and function of intestinal bacteria by binding to them. However, until now, we didn't know what could trigger IgA responses to bacteria in a dynamically changing intestinal environment.


Intestinal bacteria help us break down what we eat into smaller pieces called metabolites. Recent studies suggest that these metabolites have a significant impact on immune function in the intestinal tract. In particular, short-chain fatty acids (SCFAs), a major metabolite of intestinal bacteria, are known to be involved in creating and regulating immune-cell function. They are thought to increase IgA production, but until now, nobody knew what could trigger this behavior.


A research group fed mice food that can specifically increase SCFAs locally in the large intestine. Analysis of the mice showed that acetate, a type of SCFA, increases both the number of IgA-producing cells and the amount of IgA, and also regulates how much IgA is bound to each intestinal bacterium.


The researchers also found that the type of bacteria to which IgA binds depends on whether acetate is present or not. Normally, IgA binds mostly to common symbiotic bacteria, but in mice treated with acetate, it tended to bind to potentially harmful bacteria such as E. coli. More detailed analysis showed that when acetate leads to IgA production in the colon, the IgA binds to those potentially harmful bacteria and prevents them from settling in and invading the mucus layer.


Overall, this study revealed that acetate produced by bacteria can change the balance of IgA in the intestines. The process involves enhancing IgA production together with bacterial components. By increasing IgA production, especially IgA that will attack potentially harmful bacteria, acetate can alter the bacterial makeup of the intestines.




Tadashi Takeuchi, Eiji Miyauchi, Takashi Kanaya, Tamotsu Kato, Yumiko Nakanishi, Takashi Watanabe, Toshimori Kitami, Takashi Taida, Takaharu Sasaki, Hiroki Negishi, Shu Shimamoto, Akinobu Matsuyama, Ikuo Kimura, Ifor R. Williams, Osamu Ohara, Hiroshi Ohno. Acetate differentially regulates IgA reactivity to commensal bacteria. Nature, 2021; DOI: 10.1038/s41586-021-03727-5


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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