Immunity and infectious diseases – the key role of the microbiome
Although there has been a lot of talk and writing about the microbiome recently, not everyone knows exactly what the microbiome is or what role it plays in our body’s immune response, particularly when it comes to our immunity or the healing and recovery process.
Immunity and infectious diseases – the key role of the microbiome
The Human Microbiome Project has revealed that each microbiome contains up to 3.3 million unique protein-coding genes. This growing field of research continues to highlight the importance of the microbiome and the extent of its influence. One ongoing area of research is its relationship with immunity. It is now accepted that a balanced microbiome is crucial for the proper development and functioning of the immune system, which helps explain why 80% of our immunity is located in the gut. In 2018, researchers Libertucci and Young proposed a new function of the microbiota: the ability to shape susceptibility to infectious diseases and their outcomes.
A healthy microbiota is designed to prevent the growth, persistence and subsequent infection by foreign microorganisms (resistance to colonisation). Our native microbiota directly inhibits all pathogens through its own protective mechanisms, and indirectly assists by signalling the host’s immune system to mount a defence.
The role of the gut-associated lymphoid tissue (GALT)
The immune system of the intestinal mucosa plays a key role in this. Its defence mechanisms include: the secretion of antimicrobial peptides (AMPs) and the dynamic and adaptive production of targeted immunoglobulins in response to pathogenic threats. It is now known that the bacterial composition of our microbiome has a direct impact on all these elements.
Protein complexes, on whose quality the integrity of the intestinal barrier depends, can be impaired in the presence of certain bacteria, such as C. difficile or Yersinia enterocolitica. The amount of mucin, the main component of our mucus layer, increases in the presence of certain commensal bacteria, such as E. coli, but is degraded in the presence of, for example, C. difficile. AMP production is increased by certain commensals, such as Bacteroides thetaiotaomicron and Bifidobacterium breve, as well as in the presence of short-chain fatty acids (SCFAs). AMP (antimicrobial peptides) secreted by intestinal mucosal cells form part of our innate immune system. They protect epithelial cells by binding to and damaging the cell membranes of bacterial pathogens and by inhibiting viral replication. Another innate immune defence is secretory IgA antibodies, the secretion of which also depends on a properly functioning microbiome and may increase in the presence of certain commensal bacteria, such as Lactobacillus reuteri.
Inducing a targeted immune response
Our targeted adaptive defence against pathogens occurs through the production of antibody-producing cells (APCs). T and B lymphocytes proliferate in an area known as Peyer’s patches, located in the ileum and forming part of the GALT. Commensal gut microorganisms are essential both for the maturation of these secondary lymphoid organs and for alerting them when they need to be on the lookout for an impending threat.
This means that any disruption to the microbiome can result in altered immunity and increased susceptibility to infections. For example, the administration of antibiotics can significantly deplete the microbiome and predispose individuals to C. difficile infection. Impaired barrier function may allow lipopolysaccharides (LPS), a structural component of Gram-negative bacterial cell membranes, to be released into the bloodstream, which may continuously activate our immune system and lead to the low-grade chronic inflammation observed in many conditions.
When it comes to viruses, the interactions between them and the commensal microbiota are not so clear. We know that in healthy individuals there are groups of viruses that are not pathogenic, known as the human virome. These viruses use evasion mechanisms to enable tolerance by the immune system (a strategy unfortunately also used by pathogenic viruses) and can modulate the immune response.
The protective role of bacteria
It has been shown that certain bacteria protect against specific viral pathogens. Bacteria of the genus Lactobacillus inhibit the growth of norovirus in mice, whilst Bifidobacterium breve inhibits rotavirus. The gut microbiota may also trigger antiviral defence mechanisms in distal sites, such as the lungs. It has been shown that gut probiotics, such as Lactobacillus paracasei and plantarum, influence inflammatory responses during influenza virus infection. This is a relatively new field of research, which will undoubtedly gain momentum with the emergence of COVID-19.
Optimisation of microbial defence
So, to optimise the functioning of our microbiome to protect us against infectious diseases, there are many things we can all do. Minimising alcohol consumption, giving up smoking and managing stress will have a really positive impact. When it comes to diet, research suggests that we need to expand our diet to include a variety of plant-based foods and reduce our intake of saturated fats.
There are also certain therapeutic objectives that we can pursue: modulating the microbiome using targeted probiotics, prebiotics and polyphenols; increasing secretory IgA levels; and boosting mucin production.
The use of probiotics, prebiotics and polyphenols.
It has been shown that certain probiotics strengthen the protective barrier. A double-blind, placebo-controlled study using MegaSporeBiotic showed that 30 days of supplementation can reduce endotoxemia from leaky gut following a high-fat meal by 45%, as well as significantly lowering levels of inflammatory cytokines. (McFarlin et al., 2017) Many probiotics struggle to survive the harsh passage through the stomach, but spores can and do reach the gut fully viable, thereby producing a more lasting and stable effect. These studies suggest that spores were able to strengthen the integrity of the intestinal lining, keeping endotoxins out of the bloodstream.
Another way to beneficially modulate the microbiome is to promote the growth of keystone species, such as Akkermansia municiphilia and Faecalibacterium prausnitzii, as well as Bifidobacteria, using carefully selected prebiotics consisting of engineered oligosaccharides. It has been shown that keystone bacteria help maintain the balance of the microbiome and also improve the function of tight junctions between intestinal cells.
Other studies have highlighted the importance of polyphenols (PPs) and their metabolites in modulating the microbiome and barrier function through their antimicrobial, antioxidant, anti-inflammatory and antiproliferative effects, both at the intestinal and systemic levels. They can improve the composition of the microbiota and also counteract pro-oxidative and/or pro-inflammatory reactions.
Protection of the intestinal mucosa
Increasing the secretion of immunoglobulins, which bind to and neutralise toxins in the lumen and mucosa before they reach the intestinal epithelium, may also be effective. Nutrients have been shown to have a positive effect on their production and secretion, including essential omega fatty acids, glutathione, glycine, phosphatidylcholine, vitamin C, zinc and colostrum.
Another approach is to increase mucin production in order to strengthen the mucus layer lining the intestinal epithelium. Nutrients that have been shown to do this include the amino acids L-threonine, L-serine, L-proline and L-cysteine, where, in one study on rats, supplementation with these increased production by 95%. They are available in our MegaMucosa supplement
MegaMucosa™ – regenerator jelita
Pierwszy na rynku flawobiotyk odbudowujący śluzówkę jelit.
Summary
In summary, our microbiome plays a key role in how each of us responds to an infectious disease. However, there are steps, as described above, that we can take to boost our immune function.
The text was translated into Polish by Novolabs from the original text by Karen Jones, a practising, registered BANT nutrition therapist who provides training and support to practitioners working with Microbiome Labs products.
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