Our immune system and gut health

The best thing people can do to reduce the risk of infection and the seriousness of the illness is improve your immune system and the best thing you can do is constantly work on your gut health

Our immune system function is tightly linked to our gut microbiome. It appears the immune system is the keeper of a healthy gut microbiota which, in turn, controls our immune system. Over millions of years of evolution, our immune system has acquired elegant mechanisms for mounting immunity against pathogens and controlling the microbiome in a mutualistic, beneficial way. Gut microbiota and their metabolites can interact with both the innate immune system (these are the immune system cells that attack the foreign cells and bits in the blood) and the adaptive immune system (the second level of the immune system). We seem to have this perfect balance—at least when everything is working well. 

Throughout evolution, the first layer of the GI tract, the epithelium, has developed a complex gene network to regulate the activities of the microbiota and responses of immune cells to provide a harmonious coexistence between our immune system and GI microbiota. In healthy individuals, this network recognises good (commensal) bacteria in the mucus layer and sends signals not to attack it and to suppress inappropriate immune responses. The cells that are capable of triggering inflammation are balanced by cells that promote tolerance, protecting the body without damaging sensitive tissues. The top layer, or the intestinal cells, is always exposed to a variety of external stresses, including food-derived stimulants, environmental chemicals, intestinal micro-organisms and their toxins. The protective responses of these immune cells may, however, simultaneously induce inflammation. This type of inflammation in normal intestines is mild and controllable. However, if inflammatory reactions continue because of excessive stress or the formation of a vicious reaction cycle, disruption of the cells and dysfunction of the intestines will occur. A typical and severe example of such uncontrollable inflammation is inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis. 

While some foods and contaminants might set off an inflammatory reaction, fortunately a number of plant-based food substances such as polyphenols like curcumin and isothiocyanates from cruciferous vegetables, resveratrol from red wine, and chlorogenic acid in coffee are anti-inflammatory, antioxidative and have been shown to suppress intestinal inflammation. 

How our GI tract and immune system recognise good bacteria and viruses is at least partly established in the first few years of life. The first bacteria in our lives get the best real estate in our GI tract and are the first ones to “talk to” our immune system. That is why the prenatal (maternal) microbiota and the early life (infant) microbiota have crucial roles in the later development of immune responses, particularly in regard to allergens and foreign chemicals. Children do not develop peanut allergies because of their exposure to peanuts; they develop them because the right balance in their immune system has not been established in the first place.

When the partnership between the gut mucosal layer and the microbiome is impaired, we have a significant risk of disease. Diseases associated with abnormal immune responses toward environmental and self-antigens have been rapidly increasing over the past 50 years, especially allergies and asthma.

The gut immune system has evolved to distinguish the tiniest molecular difference that exists between pathogenic and non-pathogenic micro-organisms. It has developed the capacity to react rapidly to any harmful threats before the enemycan multiply or even before harmless bacteria may mutate into dangerous ones. In the gastrointestinal tract (GIT), the immune system contributes to the maintenance of the delicate equilibrium that exists between bacteria, yeast, bacteriophages (viruses), and gut epithelium to guarantee homeostasis and our optimal health. The immune reaction caused by an invading pathogen needs to be properly tackled, avoiding underestimations, but also without developing over-reactions that might be damaging for us. 

Because of the role of the gut in the immune system, hospital studies show an increase in the post-infection rate of intensive care patients after antibiotics as a result of a creating a positive environment for the growth of resistant opportunistic species. 

Our gut assesses what is going on through specific receptors (“toll-like receptors” or TLRs) on the gut lining which enable the immune system to sensethe environment and protect the host from pathogens or other internal threats. They recognise molecules broadly shared by pathogens collectively named as pathogen-associated molecular patterns (PAMPs). One of the most important of these PAMPs is LPS, which you will learn about shortly. The TLRs sense the potentially harmful molecules of pathogens that infect humans and switch on the bodys defence systems to react accordingly, where they activate the immune system or they inhibit the inflammatory cascade.

This is an extract from Dr Dingle’s best selling gut health book Gut Secrets https://www.drdingle.com/collections/frontpage/products/gut-secrets

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