A Healthy Immune System Could Have Roots in Your Gut

When a sudden cold leaves you coughing and sneezing, your gut microbiome is probably the last thing on your mind. The gut microbiome may significantly impact our immune system, which could be good news for those who suffer from a host of conditions, including Alzheimer’s disease, rheumatoid arthritis, inflammatory bowel disease (IBD), and asthma.

A 2014 article in Cell explored the relationship between the microbiota and our immune system. It proposed that, in high-income countries, overuse of antibiotics and changes in diet have rendered microbiomes less diverse and resilient, resulting in a sharp increase of autoimmune and inflammatory diseases over the past few decades. It is widely understood that the microbiota is intrinsic to the regulation of the immune system, and this understanding now informs research in the area.

Recent studies have linked gut health to conditions like Alzheimer’s (a neurodegenerative disease) and multiple sclerosis (a disease of the central nervous system). Scientists are still trying to figure out whether it’s the diseases that cause an imbalance in gut microbes or whether the conditions themselves could possibly stem from a shift in gut microbiota.


What does our gut have to do with autoimmune conditions?

The microbes in our guts have co-evolved with us, forming a symbiotic relationship that promotes immune homeostasis (a balanced immune system), effective immune responses, and protection against pathogen colonization. Pathogens, however, have also evolved ways to replicate within the gut microbiota. A disruption of the gut microbiome—through environmental and genetic factors—can increase the risk of pathogen infections and the development of inflammatory disease.

Our gut microbes communicate with our immune system, and research has shown that microbial exposure early in life can help protect against immune-mediated diseases, such as IBD and asthma. However, beyond childhood, there are many ways in which our gut microbiome can impact our immune systems. A number of recent studies shed light on which microbes impact immunity and how.

One study found that patients with rheumatoid arthritis (RA) had less diverse gut microbes than control groups without the disease. In the same study, gut microbial diversity correlated with disease duration and autoantibody levels. The researchers concluded that dysbiosis in RA patients likely results from a large number of certain rare bacteria. They suggested that a correlation between the intestinal microbiota and metabolic signatures could help predict who might develop RA and how the disease might progress.

Another study tested the use of the bacterium Prevotella histicola in mice. The mice treated with this bacterium had fewer and less severe cases of arthritis compared to control groups. These findings suggest that Prevotella histicola, which is native to the human gut, may suppress arthritis. P. histicola could potentially be explored as a new therapy— with few to no side effects—for RA patients.

Perhaps most promising, a Yale study of mice and humans from March 2018 found that gut bacteria can drive autoimmune disease. Researchers discovered that Enterococcus gallinarum, a bacterium that causes a number of infections, can migrate from the gut to the lymph nodes, liver, and spleen.

The researchers discovered that, in both genetically susceptible mice and in the liver cells of healthy humans, E. gallinarum initiated the production of auto-antibodies and inflammation. Using a vaccine targeted specifically at E. gallinarum, the scientists were able to suppress its growth in the tissues and blunt its effects on the immune system. Vaccinations against other bacteria were not successful at preventing mortality and autoimmunity. The authors of the study plan to further investigate E. gallinarum, and concluded that there may one day be a vaccine to improve the lives of patients with autoimmune diseases.


Healthy Gut, Healthy Immune System

There is much more research to be done, but what’s clear is that a healthy gut microbiome can aid in keeping your immune system functioning optimally. It has also been established that diet can have a significant impact on gut health and, therefore, immunity.

Doctors may prescribe dietary changes to people who are at risk for autoimmune diseases like diabetes or rheumatoid arthritis or people who’ve already been diagnosed with those conditions. Some doctors are already prescribing medical foods and nutraceuticals.

While unrelated to food, it’s important to point out that researchers have also tried applying beneficial bacterial metabolites directly to disease sites, with positive results. For example, in one study, colonic inflammation in IBD patients decreased when butyrate or Short Chain Fatty Acids cocktails were added to the colon via enema.


Immune to problems

As scientists continue to discover just how our gut microbiome impacts our immune system, one thing is clear: microbes can be our immune system’s best friends.

Want to know more about your own gut microbiome? You and your healthcare provider can use uBiome’s SmartGut testing to find out how your gut microbiome is functioning and to monitor changes in your gut flora over time.