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

Defense against intestinal infection in organism is affected by prostaglandin E2

November 15, 2018
The treatment of intestinal infections caused by some strains of the bacterium Escherichia coli, present in unsanitized or contaminated foods, may have a new ally.

No link between 'hypoallergenic' dogs and lower risk of childhood asthma

November 15, 2018
Growing up with dogs is linked to a lower risk of asthma, especially if the dogs are female, a new study from Karolinska Institutet and Uppsala University in Sweden shows. However, the researchers found no relation between ...

Researchers finds better ways to improve the chances of survival of children with a rare immune deficiency

November 15, 2018
An international study published in the journal Blood by researchers led by Dr. Elie Haddad, a pediatric immunologist and researcher at CHU Sainte-Justine and professor at Université de Montréal, highlights the urgent need ...

Human Cell Atlas study reveals maternal immune system modifications in early pregnancy

November 14, 2018
The first Human Cell Atlas study of early pregnancy in humans has shown how the function of the maternal immune system is affected by cells from the developing placenta. Researchers from the Wellcome Sanger Institute, Newcastle ...

Researchers identify factors behind inflammation in immunodeficiency patients

November 14, 2018
Oregon State University researchers have discovered two key factors behind the intestinal inflammation that plagues people suffering from a disorder that affects their immune system.

New antibody breakthrough to lead the fight against cancer

November 14, 2018
Scientists at the University of Southampton have developed a new antibody that could hold the key to unlocking cancer's defence against the body's immune system.

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.