- How does immunity work?
- From the gut to the lungs
- Coronavirus and dysbiosis
- Rebuilding the intestinal barrier
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The immune system is an extremely complex structure made up of many components. The intestinal barrier is one of them. Check how to improve its operation and help the body fight viruses.
Do you know what is the largest immune organ in the human body? It is the digestive tract. It is there that about 70% of lymphocytes are located, which are mainly arranged within the GALT lymphoid tissue. An important element of "armament" is the gut microbiota, which helps GALT to assess what is the pathogen and what is its own he althy cell. When there is a microbial imbalance in the gut (dysbiosis), the body's immune response changes and the risk of infection increases. Recent research from China shows that it may also contribute to SARS-CoV-2 infection.
How does immunity work?
There are two types of immunity: innate and acquired. When using innate immunity, the body uses two mechanisms: a physiological barrier, such as skin, mucous membranes, low pH of the stomach, microbiota with bactericidal substances (bacteriocins) produced by it, as well as with the help of phagocytic cells that "eat up" foreign substances, and mediators such as cytokines and chemokines. This system works from birth. Time is needed to develop acquired immunity. The time it takes the body to come into contact with and learn to respond to different antigens. Lymphocytes are responsible for the recognition of antigens.
The immune system is an extremely complex structure that is made up of many components. One of them is the intestinal barrier. It consists of a single layer of intestinal epithelial cells covered with a protective mucus inhabited by bacteria. The cells of the blood, lymphatic, nervous and immune systems are located under the epithelium. The barrier is an important part of several axes, incl. entero-pulmonary axis. It is a combination that is especially important for our immunity. And also here, without microbiota, there would be no question of its proper functioning. Bacterial metabolites are short-chain fatty acids (SCFA), which enable the production of immune cells. From the digestive tract, they travel to the bone marrow, where they mature, and then end up in the bloodstream, liver and lungs.
From the gut to the lungs
About the callintestines with the lungs (with the help of SCFA, hormones, peripheral nerves, cells of the hematopoietic and immune systems) is known for a long time. For example, it has been verified that there is an association between the microbiota composition in infants and the asthma phenotype later in life. In a study published a few months ago in the American Journal of Respiratory and Critical Care Medicine, it turned out that the condition of the intestinal barrier depends on the prognosis of people with upper respiratory tract infection, who are in a severe condition, connected to a ventilator in the intensive care unit. How it's possible? When the intestinal barrier is broken, the permeability of toxins increases, including those from the bacterial cell walls. The presence of the entero-pulmonary axis transports them from the intestine to the lungs. The integrity of the intestinal barrier depends, among other things, on from the proper condition of the microbiota. Caring for immunity, therefore, it is important to prevent dysbiosis. When does it happen? The problem is high-fat, the so-called Western diet, drug abuse (e.g. antibiotics, proton pump inhibitors or non-steroidal anti-inflammatory drugs), and chronic stress. Unfortunately, the latter factor is taking the lead during the coronavirus pandemic. Increased anxiety, lack of social contact, mental fatigue - all these worsen the condition of the intestines. It doesn't help that we often eat our sorrows with sweets and "junk" food or drink alcohol.
Coronavirus and dysbiosis
What about SARS-CoV-2 infection? Can the observations on the entero-pulmonary axis be transferred to this ground? Currently, there is no research on this subject, but the first retrospective conclusions after the treatment of patients are already appearing. A Chinese study by Kaijin Xu et al. Noted that some of the infected had a reduction in beneficial bacteria of the generaLactobacillusandBifidobacterium . It was recommended to introduce probiotics and prebiotics, which - by correcting the dysbiosis - could prevent the movement of microorganisms (including viruses) outside the intestines. It is not fully known how dysbiosis occurs in patients, but these observations give food for thought.
Prophylaxis in the form of strengthening the intestinal barrier is supported by the fact that SARS-CoV-2 can be transmitted not only by droplets, but also by food. Moreover, in some patients, the coronavirus causes gastrointestinal complaints in the form of diarrhea and abdominal pain, which sometimes precede the symptoms of the upper respiratory tract.
Rebuilding the intestinal barrier
To improve the functioning of the intestinal barrier, you should take care of it rich in vegetables anddietary fiber, introduce relaxation methods to minimize the damaging effects of stress and avoid stimulants. Probiotics can help in a difficult time for immunity. Some strains of the genusLactobacillus(e.g. Lactobacillus acidophilusW37 , Lactobacillus brevisW63), Bifidobacterium(e.g.Bifidobacterium bifidumW23 , Bifidobacterium lactisW52) andLactococcus (e.g.Lactococcus lactisW19 , Lactoccous lactisW58) have a proven barrier-strengthening effect.
Rebuilding the intestinal barrier takes place in many fields, because bacteria stimulate both innate and acquired immunity. To make the barrier more tight, probiotic bacteria increase the production of protective mucus, regenerate intestinal epithelial cells with short-chain fatty acids (SCFA), and also produce cytoprotective compounds. Besides, thanks to the presence of the "good" bakery, the number of pathogens is reduced, because they not only literally take the place of the "bad" in the gut, but also take away their nutrients. In addition, they increase the production of antimicrobial substances that directly "knock out" the other side. An important function of probiotic strains is to enhance the anti-inflammatory response - and so bacteria increase, for example, the secretion of anti-inflammatory interleukin 10 (IL-10), which inhibits pro-inflammatory cytokines. In this way, probiotics provide prophylaxis at the same time at the level of the intestinal epithelium, microbiota and GALT.