How good bacteria can help keep a gut healthy

July 3, 2018, Baylor College of Medicine
Credit: CC0 Public Domain

New research reveals a cellular mechanism by which good bacteria can help the gut stay healthy. The study, which appears in the journal Immunity, shows that good bacteria, or the microbiota, interact with both the epithelial cells lining the gut and cells of the immune system to help balance the immune responses and protect the gut from unwanted inflammation. The study suggests that manipulating the microbiota to limit intestinal immune responses could have potential therapeutic benefits for conditions such as inflammatory bowel disease.

"A significant body of work currently indicates that the shapes the immune system and helps it to do its job," said corresponding author Dr. Gretchen Diehl, assistant professor of molecular virology and microbiology co-director of the Biology of Inflammation Center and a member of the Dan L Duncan Comprehensive Cancer Center at Baylor College of Medicine. "Disease-causing microbes, such as Salmonella, evoke a strong inflammatory immune response that is directed at eliminating the microbe. But an inflammatory immune response, especially in the intestine, can be damaging to the healthy tissue. Here we defined a role for the microbiota in modulating the immune response in a way that reduces inflammation and limits the damage it can do to the gut."

For an effective immune response, called antigen-presenting cells direct other immune cells, called T cells, to mount an appropriate to fight microbial invaders. They also direct anti-inflammatory T cells, also known as regulatory T cells, to limit inflammatory immune responses against things like the food we eat and to turn off inflammatory immune responses.

The microbiota helps 'tune down' the inflammatory response by instructing the antigen-presenting cells to secrete the cytokine IL-10, an important anti-inflammatory molecule. IL-10 dampens inflammatory T cell responses and promotes regulatory T cell responses that keep the balance.

"The result is a balanced response that still can fight off an infection like Salmonella, but that is regulated to prevent damage to the healthy intestinal tissue," Diehl said. "We wanted to know how the microbiota could induce these kind of responses."

The microbiota-epithelium connection

"We found that when we gave the laboratory animals antibiotics, the antigen-presenting cells did not make IL-10. When we put back bacteria in the animals' guts, only bacteria that could attach to the intestinal epithelium triggered IL-10 production by and reduced the inflammatory response," Diehl said. "It's somewhat counterintuitive because microbes that can attach to the intestinal epithelium are thought of as pathogens that can potentially cause disease. But in this case we found that the attachment of bacteria to the epithelium was not causing disease; on the contrary, it was necessary to promote a balanced regulation of the T and helped protect the gut."

The researchers indicate that their study is barely scratching the surface, and they are actively looking for other mechanisms by which microbes can promote a well-balanced intestinal environment.

Next, Diehl and her colleagues also plan on investigating the signaling pathways that are activated when the microbes attach to the to identify novel pathways for inducing a balanced .

"A take home message for us is that a healthy microbiota is necessary to allow for a balanced to not only protect us from infection, but also to limit potential tissue damage as the immune system attempts to eliminate pathogens," Diehl said.

Explore further: Innate lymphoid cells play an important role in regulation of intestinal inflammation

More information: Myunghoo Kim et al, Critical Role for the Microbiota in CX 3 CR1 + Intestinal Mononuclear Phagocyte Regulation of Intestinal T Cell Responses, Immunity (2018). DOI: 10.1016/j.immuni.2018.05.009

Related Stories

Innate lymphoid cells play an important role in regulation of intestinal inflammation

August 28, 2017
The intestine contains an extensive and diverse microbial biome, a population that includes potential pathogens and dietary antigens that need to be tolerated. Dysregulation of mucosal responses may cause a loss of tolerance, ...

New research suggests more sensitive approaches to detect and monitor inflammatory bowel disease

May 15, 2017
A University of Manchester test on the mucus lining of the intestine, performed in mice, has found changes in bacteria that could lead to inflammatory bowel disease 12 weeks earlier than previously possible through looking ...

The early cost of HIV: Inflammatory response breaks down intestinal lining, but help may come from friendly bacteria

August 30, 2014
Researchers at UC Davis have made some surprising discoveries about the body's initial responses to HIV infection. Studying simian immunodeficiency virus (SIV), the team found that specialized cells in the intestine called ...

Immune cells' bacteria may fight chronic inflammation

March 17, 2016
A population of bacteria inhabits human and mouse immune cells and appears to protect the body from inflammation and illness, Weill Cornell Medicine scientists discovered in a new study. The findings challenge conventional ...

Researchers identify unforeseen regulation of the anti-bacterial immune response

August 28, 2012
New research from the laboratory of Dr. Andrea Cooper at the Trudeau Institute, just published in the European Journal of Immunology, holds promise for the improved prevention and treatment of bacterial infections and the ...

Recommended for you

Team explores diabetes drug's ability to treat RSV infection

July 13, 2018
A drug used to treat diabetes may point to new therapies for respiratory syncytial virus (RSV) bronchiolitis—inflammation and obstruction of the lungs' small airways. A multi-disciplinary team of Vanderbilt investigators ...

Testing suggests TORC1 inhibitors can boost immune system in the elderly

July 12, 2018
A team of researchers affiliated with Novartis Institutes for Biomedical Research and Biometrics Matters Limited, has found via testing with volunteers that TORC1 inhibitors can boost the immune system in the elderly. In ...

Biologists discover process that neutralizes tumors

July 10, 2018
Researchers from the University of California San Diego have identified an unexpected mechanism that could help determine whether a cancer patient will respond to immunotherapy.

Mitochondrial DNA in exosomes is the alarm that initiates the antiviral response

July 10, 2018
Researchers at the Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC) have provided valuable information about the defense mechanisms of the immune system during the early stages of the response to pathogens ...

Antibody identifier could speed development of therapies for cancer, other diseases

July 10, 2018
A research team led by a UCLA bioengineer has developed a model to predict the extent to which new laboratory-designed antibodies will be able to combat specific human diseases. This is the first time that a comprehensive ...

Immune cells can switch from 'gang members' to 'police officers'

July 10, 2018
When the immune system overreacts, as in an allergic reaction, cells causing trouble can change into cells that dampen the reaction.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.