Intestinal flora affects our immune system
There are as many intestinal bacteria in our body as there are cells. The microbiome in the gut consists of trillions of microorganisms. Recent research shows that this community is not only responsible for digestion but also plays an important role in our immune system. An intestinal flora is even essential for a healthy immune system, as a new study shows.
Researchers at the University of Bern were able to understand for the first time how certain intestinal bacteria stimulate white blood cells to produce antibodies. This important defense process can take place before the blood cells hit the real pathogen. The results were recently presented in the famous magazine “Nature”.
How our immune system fights pathogens
So-called B cells in our immune system are responsible for the detection of foreign substances. The cells belonging to the white blood cells ensure that appropriate antibodies are produced to fight the relevant pathogen. The antibodies in turn bind to the invaded viruses or bacteria to render them harmless.
What role do intestinal bacteria play in the immune system?
The research team led by Professor Stephanie Ganal-Vonarburg and Professor Andrew Macpherson has now shown that intestinal bacteria play a much greater role in the immune process than previously thought. On the one hand, the intestinal microbes ensure an accumulation of B cells and, on the other hand, they can trigger the production of antibodies even before the B cells have come into contact with a pathogen.
Intestinal bacteria also reach other parts of the body
A large part of the intestinal bacteria remains permanently in the intestine. “However, a certain amount of penetration into the bloodstream is unavoidable, because the intestine has only a single layer of cells that separates the inside of the intestinal tract from the blood vessels that we need to eat,” explains Stephanie Ganal-Vonarburg. In the current research work, the team followed for the first time the pathway that takes intestinal bacteria inside and outside the intestine and what influence this has on the immune system’s B cells.
B cells respond to intestinal bacteria
Using the latest computer technology, millions of genetic sequences can be processed and compared. In this way, reactions from the B cells to bacteria from the intestine can also be documented. The reactions to the bacteria seem to vary depending on whether they stayed in the intestine or entered the bloodstream. “In both cases, the antibody repertoire changes, but in different ways,” adds Andrew Macpherson.
“This indicates that the gut bacteria control the development of our antibodies before we get a serious infection, and that this process is certainly not unintentional,” the professor emphasizes.
How do immune responses differ?
The researchers also found that different antibodies dominate in the gut than in the rest of the organism. The range of the various antibodies produced in the gut is much smaller than outside the gut. “This means that as soon as harmful bacteria enter the body, there are many more ways to fight them, while antibodies in the gut only bind the harmful bacteria they encounter,” Ganal-Vonarburg explains.
In the further study, the team examined how the immune system of aseptic mice inside and outside the gut reacts to certain pathogens. The mice were brought into contact with two different pathogens in two waves. With the first pathogen, the same antibodies were formed in the gut and in the rest of the body to fight the pathogen. However, the other pathogen showed a fantastic event.
Intestinal bacteria stimulate the memory of the immune system
In the gut, the antibodies were altered to respond to the other pathogen. Thereafter, only the antibody for the other pathogen was produced there – “similar to when the lock was replaced in a door”, the team describes the process. However, if these intestinal bacteria entered the bloodstream, the antibodies from the first pathogen were also produced, which is more like installing an extra lock. “This shows that the immune system remembers different types of harmful bacteria and can avoid the risk of blood poisoning,” Macpherson emphasizes.
“We were able to show for the first time that not only the composition of our intestinal flora, but also how it encounters B cells in the body has a different influence on their antibody repertoire and the subsequent immunity to pathogens,” concludes Hai Li, one of the study authors. (Vb)
Also read: Build gut flora: How it works.
Author and source information
This text complies with the requirements of the medical literature, medical guidelines and current studies and has been checked by medical staff.
Diploma-Editor (FH) Volker Blasek
- University of Bern: Intestinal bacteria «program» our antibodies (published: 05.08.2020), unibe.ch
- Hai Li, Julien P. Limenitakis, Victor Greiff, u: Mucous membranes or systemic microbial exposures form the B-cell repertoire; in: Nature, 2020, nature.com
This article contains general information only and should not be used for self-diagnosis or treatment. He can not reimburse a visit to the doctor.