covid-19 gut bacteria and immune system

Gut Bacteria and Immune System: How Are They Connected?

Our gut bacteria and immune system go way back…to the womb. They’ve developed complex checks and balances that see us through adulthood. Learn how gut bacteria and immune system cells communicate.
Out gut bacteria and immune system cells are OGs. They go way back to the womb. This lifelong friendship continues with us through birth, during life, and until we breathe our last breath. So, how did gut bacteria and immune system cells become besties? Let’s discuss the science behind our immune system and gut bacteria communication and how improving your gut health can boost your immune system naturally.


Gut Bacteria and Immune System at Birth

Our bodies host trillions of microbes that vary from fungi to viruses to bacteria. They are comprised of cell clusters. The space in which these beings coexist is called the microbiome [1].

gut bacteria and immune system birth

Not so shockingly, our mothers are also made of microbes. Therefore, her microbes were the first living beings you were in contact with. She also provides you with antibodies, food, and oxygen to grow. As a foreign being takes residence in her womb, her microbes investigate. After they realize that a beautiful life is forming, they help form your immune cells.
Once the delivery process begins, lifelong connections are made. These connections are just between mother and child. They’re between your immune cells and stomach bacteria.
As you make your descent into this world, you become introduced to your mom’s gut bacteria. Scientists believe that the placenta doesn’t have much bacteria [2]. So, this process is critical to providing a baby with gut bacteria and immune system cells that will support them outside of the womb.


How The Immune System Works


Our immune system is designed to attack intruders and concoct game plans, so these bad guys don’t return. The first line of defense is the innate immune system. These cells usually create inflammation at the first sign of any predator. Once the threat is extinguished, the inflammation ceases.

Innate vs. Adaptive Immune System
The adaptive immune system plays a long-term game. They learn the weaknesses of viruses and opportunistic bacteria. Then, they create antibodies to stop future infestations.


Why Gut Bacteria and Immune System Are Connected

When we’re dealing with toxins and food waste, you’re going to need a lot of immune cells. That’s why approximately 80% of our immune cells exist in the gut [3].

Our gut barrier is made of epithelial cells. They protect our healthy microbes and immune system cells from toxins and waste waiting to exit our intestines.
Whenever we eat, our food choices can cause a number of problems. If we eat an allergen, such as gluten, it may cause inflammation. The more we consume this allergen, the more inflammation it causes.
Over time, this inflammation destroys the epithelial cells, causing toxins to leak into the system. In the end, we develop Leaky Gut Syndrome.
In the same breath, eating foods devoid of prebiotics can starve off gut bacteria. Without beneficial gut bacteria, you have nothing to help you digest food, absorb nutrients, and fight off pathogens. This reaction adds stress on our immune system. Therefore, it’s everyone’s best interest to keep the other party happy.


How Gut Bacteria and Immune System Communicate

Since they’re neighbors with the same agenda, it’s a good idea for your gut bacteria and immune system cells to communicate. Research shows that they actually have an intricate and effective communication system. They use the gut barrier as their call line.
Both gut bacteria and immune system cells have an invested interest in maintaining the gut barrier. Therefore, they both contribute components to its structure that improve its functioning.
One meta-analysis of gut barrier structuring noted,

“The physical intestinal barrier consists of a continuous single layer of columnar epithelial cells overlain by a variably thick layer of mucus. This mucus layer is embedded with antibodies and antimicrobial peptides and physically separates the epithelium from direct contact with much of the luminal microbiota [4].”

Front Immunol

Both immune and epithelial cells have antimicrobial capabilities that help protect the microbiome. However, this is just the beginning of their symbiotic relationship.


How Microbes Communicate Along Gut Barrier

sensors gut bacteria and immune system

Epithelial cells monitor intestinal flora because they are equipped with immune receptors known as pattern-recognition receptors (PRRs) [5]. Based on the bacteria, epithelial cells adjust their microbial activity.
The gut barrier is further regulated by gut bacteria in our microbiome and fermenting in our intestines. Beneficial gut bacteria create waste in the form of short-chain fatty acids.
Short-chain fatty acids are like a One-Hour Energy for epithelial cells. They modulate functions, including allowing nutrients to leave the intestines and enter the bloodstream. In the case of butyrate, this short-chain fatty acid helps repair epithelial cells.


How Immune Cells Communicate Along Gut Barrier

Mast cells (M cells) are located within the gut-associated lymphoid tissue (GALT) inside our small intestine [6]. These cells take antigens of potential microbial threats and transport them through the epithelial cells. These cells then initiate an immune response to deal with potential threats.
Within our intestinal wall are also dendritic cells. These cells report back to T-cells of our adaptive immune system [7]. These communicators probe intestinal lumen in search of potential threats. That way, our immune system already has a defense before these threats get out of hand.
Also, our intestinal wall contains TH17 helper cells. TH17 cells stimulate epithelial cells to produce antimicrobial agents [8]. They also call for backup in the form of Immunoglobulin A (IgA).


IgA and Gut Bacteria

One of the most intricate interactions between gut bacteria and immune system cells is how Immunoglobulin A (IgA) interacts with intestinal flora. B cells within our adaptive immune system create this antibody as a response to potential pathogens.


IgA Influence on Stomach Bacteria


IgA can cut off danger before it begins. These immune cells can bind to food particles that cause inflammation or opportunistic microbes that may harm the microbiome [9].
In fact, IgA may influence microbial:
• Composition
• Gene Expression
Having IgA cells present can help make your gut bacteria more robust. It can seek out growing species and slowly break them down, inhibiting their growth. The gut bacteria appreciate these checks and balances. So, they show the same respect for IgA.


Stomach Bacteria Influence on IgA

IgA is derived from plasma cells created by B cells. Gut bacteria can regulate how many of these cells are within the microbiome.
Furthermore, gut bacteria try to prohibit too much inflammation. Their pro-inflammatory stance helps keep IgA levels in check. This trait not only saves gut bacteria but also helps the immune system better manage its resources.
We all have different things that set off our gut health or immune system. Some of might have a penchant for milk but are lactose intolerant. Meanwhile, someone else is who is lactose intolerant might not care for dairy anyway.


How to Improve Gut Bacteria and Immune System

Now, add in other potential issues and tastes like legume lovers with lectin sensitivities. A family grown on pasta can develop gluten problems. The list goes on and on!
Fact is, there is no one-size-fits-all approach to wellness. Your immune system and gut bacteria are unique. So, you need a custom approach.
Test your gut bacteria and get insights into your immune system with Thryve. Based on the results, we can recommend a custom probiotic targeted to provide support for the immune system. Furthermore, we can give you insights on which foods are compromising your particular immune system, and which ones will boost it up!


Click Here To View Resources



[1] Institute of Medicine (US) Food Forum. The Human Microbiome, Diet, and Health: Workshop Summary. Washington (DC): National Academies Press (US); 2013. 2, Study of the Human Microbiome. Available from:
[2] BawaganJul, Juanita, et al. “Babies Get Critical Gut Bacteria from Their Mother at Birth, Not from Placenta, Study Suggests.” Science, 31 July 2019,
[3] Vighi, G., Marcucci, F., Sensi, L., Di Cara, G., & Frati, F. (2008). Allergy and the gastrointestinal system. Clinical and experimental immunology, 153 Suppl 1(Suppl 1), 3–6.
[4] Andrews, C., McLean, M. H., & Durum, S. K. (2018). Cytokine Tuning of Intestinal Epithelial Function. Frontiers in immunology, 9, 1270.
[5] Pott J, Hornef M. Innate immune signalling at the intestinal epithelium in homeostasis and disease. EMBO Rep. 2012;13(8):684‐698. doi:10.1038/embor.2012.96.
[6] Ohno H. (2016). Intestinal M cells. Journal of biochemistry, 159(2), 151–160.
[7] Rimoldi M, Chieppa M, Vulcano M, Allavena P, Rescigno M. Intestinal epithelial cells control dendritic cell function. Ann N Y Acad Sci. 2004;1029:66‐74. doi:10.1196/annals.1309.009.
[8] McAleer, J. P., & Kolls, J. K. (2011). Mechanisms controlling Th17 cytokine expression and host defense. Journal of leukocyte biology, 90(2), 263–270.
[9] Pabst, O., Slack, E. IgA and the intestinal microbiota: the importance of being specific. Mucosal Immunol 13, 12–21 (2020).

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