Featured Research

from universities, journals, and other organizations

DNA Of Good Bacteria Drives Intestinal Response To Infection

Date:
October 4, 2008
Source:
NIH/National Institute of Allergy and Infectious Diseases
Summary:
A new study shows that the DNA of so-called "good bacteria" that normally live in the intestines may help defend the body against infection.

A new study shows that the DNA of so-called "good bacteria" that normally live in the intestines may help defend the body against infection.

The findings, available Oct. 2 online in the journal Immunity, are reported by Yasmine Belkaid, Ph.D., and her colleagues in the Laboratory of Parasitic Diseases at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

A person normally has 300 to 500 species of beneficial bacteria, known as commensals, in their intestines. These bacteria are not harmful and, in fact, help an individual maintain his or her digestive health. Typically, the immune system does not attack gut commensals, even though they are bacteria.

"Within the body of a healthy adult, microbial cells vastly outnumber human cells. Research to understand these microbial communities is an exciting scientific frontier," says Anthony S. Fauci, MD, NIAID director. "Among many opportunities related to the so-called 'microbiome,' targeting beneficial bacteria may offer new avenues for therapy against infectious and immune-mediated diseases."

Just how commensals protect against harmful bacteria, known as pathogens, is a complex question. "Pathogens often behave similarly to gut commensals," Dr. Belkaid says. Because the body needs commensals but also has to rid itself of disease-causing microbes, the immune system must distinguish the good bugs from the bad ones.

One mechanism of protection is through the interaction between the commensals and certain immune cells in the intestines. This interaction occurs through the binding of the commensals to receptors on the T cells known as Toll-like receptors (TLRs).

In healthy individuals, some intestinal T cells (known as Tregs) play a regulatory role, recognizing commensals and keeping the immune system from attacking them. During an infection, however, T cells shift into attack mode to fight the infection. The factors controlling this shift from defense to offense have not been well understood.

Dr. Belkaid's team describes a novel way in which the Tregs are regulated to facilitate an immune response to a pathogen. They found that during an infection, the DNA of the body's beneficial bacteria binds to a specific receptor on the intestinal immune cells, called TLR9. The binding of commensal DNA to TLR9 in the presence of a pathogen prevents the generation of Tregs in favor of the generation of protective T cells. These protective T cells can then clear the body of the invading pathogen.

In effect, the commensal DNA acts as a natural adjuvant by boosting the activity of T cells so they can destroy the invading pathogen.

"There is a balance of regulatory immune signals in the body," notes Dr. Belkaid. "During an infection, we've found that commensals can break this balance in favor of an infection-fighting response."

While the immune system must react to invading pathogens to maintain health, an immune response to commensals can cause problems. For example, certain inflammatory bowel diseases, such as Crohn's disease, are thought to be caused in part by immune reactions against commensal bacteria.

Understanding how commensals interact with the immune system opens up the possibility of using beneficial bacteria as targets for future oral therapies against infections or autoimmune diseases.


Story Source:

The above story is based on materials provided by NIH/National Institute of Allergy and Infectious Diseases. Note: Materials may be edited for content and length.


Journal Reference:

  1. JA Hall et al. Commensal DNA limits regulatory T cell conversion and is a natural adjuvant of intestinal immune responses. Immunity, DOI: 10.1016/j.immuni.2008.08.009

Cite This Page:

NIH/National Institute of Allergy and Infectious Diseases. "DNA Of Good Bacteria Drives Intestinal Response To Infection." ScienceDaily. ScienceDaily, 4 October 2008. <www.sciencedaily.com/releases/2008/10/081002172540.htm>.
NIH/National Institute of Allergy and Infectious Diseases. (2008, October 4). DNA Of Good Bacteria Drives Intestinal Response To Infection. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2008/10/081002172540.htm
NIH/National Institute of Allergy and Infectious Diseases. "DNA Of Good Bacteria Drives Intestinal Response To Infection." ScienceDaily. www.sciencedaily.com/releases/2008/10/081002172540.htm (accessed October 22, 2014).

Share This



More Health & Medicine News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Working Mother (Oct. 22, 2014) Is your child ready? Video provided by Working Mother
Powered by NewsLook.com
U.S. Issues Ebola Travel Restrictions, Are Visa Bans Next?

U.S. Issues Ebola Travel Restrictions, Are Visa Bans Next?

Newsy (Oct. 22, 2014) Now that the U.S. is restricting travel from West Africa, some are dropping questions about a travel ban and instead asking about visa bans. Video provided by Newsy
Powered by NewsLook.com
US to Track Everyone Coming from Ebola Nations

US to Track Everyone Coming from Ebola Nations

AP (Oct. 22, 2014) Stepping up their vigilance against Ebola, federal authorities said Wednesday that everyone traveling into the US from Ebola-stricken nations will be monitored for symptoms for 21 days. (Oct. 22) Video provided by AP
Powered by NewsLook.com
Doctors Help Paralysed Man Walk Again, Patient in Disbelief

Doctors Help Paralysed Man Walk Again, Patient in Disbelief

AFP (Oct. 22, 2014) Polish doctors describe how they helped a paralysed man walk again, with the patient in disbelief at the return of sensation to his legs. Duration: 1:04 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins