BY Benjamin Makeham March 31, 2020
The gastrointestinal system is home to approximately 70% of the body’s immune cells
Just like the skin, the gastrointestinal system is another direct point of contact with the outside world. Therefore, in order to protect our internal bodies from invading pathogens, a dense layer of immune cells lies just beneath the intestinal epithelial cells that make up the surface of the digestive tract.
However, these immune cells don’t just defend against pathogens; they are in constant communication with our community of beneficial microbes, including bacteria, viruses and fungi.
Many health-promoting metabolites are produced by our community of beneficial bacteria as by-products of metabolic reactions, such as fermentation of dietary fibre which produces short chain fatty acids. These metabolites are released by microbes and enter the intestinal lumen where they interact with receptors on both intestinal and immune cells.
There is mounting evidence to suggest that these interactions modulate the immune system and keep it in check, preventing it from overreacting while also maintaining a strong defence against harmful microbes.
It has also been observed that they have the ability to alter immune cell differentiation, keeping the many different types of immune cells at appropriate levels, and influence the type of cytokines secreted by them which in turn regulates inflammation levels also necessary for strong immunity.
In this way, the microbiota is thought to influence how the immune system operates.
The impact of the microbiota on the immune system may occur at the gut, but the effects are believed to be systemic. When these immune cells enter circulation through blood and lymph, they travel to many distant organs, such as the lungs, and transfer their beneficial effects to the entire body.
This is why it's so important to take care of our gut microbiota, because they take care of us.
Maldonado Galdeano C, Cazorla SI, Lemme Dumit JM, Vélez E, Perdigón G. Beneficial Effects of Probiotic Consumption on the Immune System. Ann Nutr Metab [Internet]. 2019;74(2):115–24.
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