Intestinal Bacteria and the Immune System

Intestinal Bacteria and the Immune System

The medical community has known for a long time that the bacteria in our intestines is important for a healthy body.  With the emergence of antibiotics, we have seen that overuse of these types of medications can lead to severe health consequences, especially from depleting the bacteria in our intestinal tract.  From yogurt to probiotics, more people are trying to get their daily dose of “good” bacteria as a means of improving intestinal health. But more recent research has shown that all of those beneficial bacteria may play an even bigger role than originally thought.

Autoimmune diseases are diseases in which the body’s own immune cells attack normal healthy “self” cells, and they have been on the rise in the last couple of decades.  Though we know a lot about how autoimmune diseases cause disease or dysfunction in the body, we know little about what in the body causes autoimmune disease to occur.  Is there a single trigger that causes the immune cells to go haywire and attack normal cells, or is it a culmination of genetics, environmental exposure and lifestyle factors?   Researchers have begun to strongly suspect the intestinal tract as a potential trigger.

Intestinal inflammation is common in autoimmune diseases, and there are a significant number of autoimmune diseases that reside directly in the gut including celiac disease, Crohn’s disease, and ulcerative colitis.  We also know that a large part of our immune system resides in and around the intestinal wall. These immune cells help to protect our body from potential toxins or foreign invaders that we may eat along with our food.   Just as bad microbes entering a wound in our skin can lead to a serious infection, toxic microbes in our intestines could cause serious damage if the immune system wasn’t nearby to address them.

However, what we have discovered recently goes far beyond the idea of a wall of soldiers  protecting our intestinal border.  New studies have shown that the healthy state of our gut can actually influence the way in which our entire immune system behaves.

A recent study that was published this summer in the journal, Nature, showed that B-cells, a type of immune cell that produces antibodies, may be produced and matured in the intestines.  B cells were commonly thought to only be produced in the bone marrow, where they grow up and are “trained” to perform a certain function.  The newer studies are supporting the idea of concurrent B cell maturation in the intestines.  It is in the intestinal lining where they start to learn how to react to foreign invaders and how to develop antibodies to fight against these microbes.  The study also showed that normal, healthy bacteria in the intestinal tract boosted development of B cells by at least 20%, a potentially huge influence on the way that our immune system functions.

A second study recently published in the journal, Science, helped to explain another newly-identified effect of gut microbes on the immune system.  The researchers looked at T-cells, which are immune cells that have been commonly thought of as problematic in certain autoimmune diseases.  This study showed that bacteria in the gut that broke down dietary fiber into particles called short-chain fatty acids have the ability to increase the number and function of a type of regulatory T-cell.  An increase in the number of these particular T-cells has been shown to decrease inflammation in the intestines and help with diseases such as Crohn’s disease.  The Multiple Sclerosis Society also feels that this may have implications for MS as well, and are optimistic that this study might fuel others to look for ways in which the intestinal bacteria can positively influence the immune system.

Although this research is relatively new, creating a healthy gut has always been important for improving overall health.  If you have questions about how you can improve the health of your intestinal tract, our doctors can help.

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