Intestinal flora influences our immune defense
There are as many intestinal bacteria in our body as there are cells. The microbiome in the gut consists of trillions of microorganisms. The latest research shows that this community is not only responsible for digestion, but also plays an important role in our immune system. The intestinal flora is even essential for a healthy immune system, as a recent 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 actual pathogen. The findings were recently published in the renowned specialist journal “Nature” presented.
How our immune system fights pathogens
So-called B cells in our immune system are responsible for recognizing foreign substances. The cells belonging to the white blood cells ensure that suitable antibodies are produced to fight the relevant pathogen. The antibodies in turn bind to the invaded viruses or bacteria in order to render them harmless.
What role do gut 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 far greater role in the immune defense process than previously assumed. 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 get to 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 inevitable because the intestine has only a single layer of cells that separate the inside of the intestinal tube from the blood vessels that we need to eat,” explains Stephanie Ganal-Vonarburg. In the current research work, the team for the first time followed the path that intestinal bacteria travel inside and outside the intestine and what influence this has on the B cells of the immune system.
B cells respond to gut bacteria
With the help of the latest computer technology, millions of genetic sequences could be processed and compared. In this way, reactions of the B cells to bacteria originating from the intestine could also be documented. The reactions to the bacteria appear to differ depending on whether they remained in the intestine or entered the bloodstream. “In both cases, the antibody repertoire is changed, but in different ways,” adds Andrew Macpherson.
“This indicates that the intestinal bacteria control the development of our antibodies before we get a serious infection, and that this process is certainly not accidental,” emphasizes the professor.
How do the immune reactions differ?
The researchers also found that different antibodies predominate in the gut than in the rest of the organism. The range of different antibodies that are produced in the intestine is much smaller than outside the intestine. “This means that as soon as harmful bacteria enter the body, the immune system has many more options to fight them, while antibodies in the intestine mainly only bind those harmful bacteria that they encounter,” explains Ganal-Vonarburg.
In the further course of the study, the team investigated how the immune system of germ-free mice reacts to certain pathogens inside and outside the intestine. The mice were brought into contact with two different pathogens in two waves. The first pathogen produced the same antibodies in the intestine and in the rest of the body to fight the pathogen. With the second pathogen, however, an astonishing event occurred.
Intestinal bacteria stimulate the memory of the immune system
The antibodies in the gut changed to respond to the second pathogen. Then only the antibody for the second pathogen was produced there – “similar to when the lock is changed in a door”, the team describes the process. However, if these intestinal bacteria got into the blood, the antibodies of the first pathogen were also produced, which is more like installing an additional lock. “This shows that the immune system can remember various harmful types of bacteria and avoid the risk of blood poisoning,” Macpherson said.
“We were able to demonstrate for the first time that not only the composition of our intestinal flora, but also the way in which it encounters B cells in the body have a different influence on their antibody repertoire and the subsequent immunity to pathogens,” sums up Hai Li, one of the study authors. (vb)
Also read: Build up intestinal flora: this is how it works.
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Diploma-Editor (FH) Volker Blasek
This article contains general information only and should not be used for self-diagnosis or treatment. He can not substitute a visit at the doctor.