Table of ContentsView AllTable of ContentsAutoimmune DiseaseAutoinflammatory DiseaseGut MicrobiomeGeneticsAssociated ConditionsTriggersCategorization
Table of ContentsView All
View All
Table of Contents
Autoimmune Disease
Autoinflammatory Disease
Gut Microbiome
Genetics
Associated Conditions
Triggers
Categorization
Although people with Crohn’s disease may produce antibodies, it is unclear whether antibodies are involved in the disease process. For that reason, it’s not accurate to call Crohn’s disease an “autoimmune” condition. Researchers who study IBD are now shifting to referring to it as an immune-mediated condition or anautoinflammatorycondition.
Crohn’s diseaseis one form ofinflammatory bowel disease (IBD). It primarily affects thedigestive system, causing inflammation. Ulcers and inflammation from Crohn’s disease can occur anywhere in the digestive system and affect other parts of the body, including the skin, joints, and eyes. It is a lifelong condition that can’t be cured.
Scientists do not knowwhat causes Crohn’s disease, but it does appear to be hereditary with an environmental trigger. There has been some research that tries to understand how to classify Crohn’s disease. As more research is completed, understanding what causes IBD will improve, leading to better treatments and individualized medicine.
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What Is an Autoimmune Disease?
When the immune system works well, most people don’t notice that it’s there or doing its job because the main function is to prevent illnesses.
However, things can go wrong with the immune system. There are several theories about how autoimmune conditions develop. One of the main ideas is that an event spurs the adaptive immune system to spring into action—such as an infection from a virus, for example.
The adaptive immune system develops and learns over time to target specific things that invade the body and cause disease. Sometimes it can mistakenly see the body’s own cells as invaders and attack them. Healthy tissue suddenly becomes the enemy, and this can lead to autoimmune conditions.
When the immune system goes haywire in this way, it can lead to a chain reaction that spurs the creation ofantibodiesagainst components of a person’s cells rather than invaders. These are called autoantibodies.
The autoantibodies play a role in causing the inflammation associated with autoimmune diseases. This is why some autoimmune conditions are treated with medications thatsuppress parts of the immune system. Tests can identify specific antibodies, but not everyone who has autoantibodies will develop an autoimmune disease.
However, no antibody has been identified to be associated with Crohn’s disease. No blood test can find the “Crohn’s” antibody and diagnose the disease, as is the case for other autoimmune conditions.
There are more than 80 identified autoimmune diseases. They run the gamut from those that are more common, such asceliac diseaseandrheumatoid arthritis, to rare conditions such asKawasaki diseaseandmyasthenia gravis.
Many autoimmune disorders are chronic and require treatment throughout a person’s lifetime. Some, however, can be self-limiting or might be treated effectively, so they don’t require continuous management. Autoimmune conditions tend to affectwomen more oftenthan men.
What Is an Autoinflammatory Disease?
Like any other type of gene, the genes that encode for the innate immune system can sometimes undergo changes. These changes can affect how the immune system reacts.
In some cases, this could mean that the innate immune system cannot tell the difference between healthy tissue that is part of the body and a substance that needs to be attacked. When the innate immune system mistakenly thinks that body cells are foreign invaders, it goes on the offensive and causes inflammation.
Crohn’s and the Gut Microbiome
Another factor to consider in the development of Crohn’s disease is how all the microorganisms that live in the digestive system (called the microbiome) play a role. It’s known that people with Crohn’s disease do not have the same balance of healthy strains of bacteria in their gastrointestinal (GI) tracts as people who don’t live with the disease.
One of the reasons it has been so difficult to understand the causes of IBD is that the microbiome is complex and not yet well understood. It’s not a matter of one or even a few strains of bacteria being either too numerous or not numerous enough.
There are, however, trends seen in the microbiome shift in people who live with Crohn’s disease. This helps get closer to understanding a cause and developing treatments, but it’s clear that not every case of Crohn’s disease affects the microbiome in the same way.
This ties into the immune response because it’s also thought that in IBD the immune system might be mistakenly attacking normal bacteria in the gut. This has been described as a “breakdown in relations” between the bugs living in the gut and the immune system.
Over time, it’s thought that chronicdysbiosis(which refers to a lack of balance in the microbiome) is one of the factors that lead to the development of Crohn’s disease.
Genetics, Crohn’s, and Autoinflammatory Disease
It’s now also known that Crohn’s disease has a genetic component. Hundreds of genes are connected to the various forms of IBD.
That makes Crohn’s a condition that can be inherited, but not everyone with the genes will develop the disease. In fact, most people who live with Crohn’s disease don’t have a relative who has the disease.
Changes in the genetics of the innate immune system play a role in the development of Crohn’s disease, but that’s not the only piece of the puzzle. There is also an environmental trigger—something that causes the innate immune system to start the inflammatory process and not stop. It’s thought that there could be many different triggers that contribute to IBD.
According to Marla Dubinsky, MD, professor of pediatrics at Mount Sinai School of Medicine and chief of the division of pediatric gastroenterology at Mount Sinai Kravis Children’s Hospital, “IBD actually fits into the category of autoinflammatory conditions, which is distinct from an autoimmune condition.”
Dr. Dubinsky said that in Crohn’s disease, “…the innate immune system becomes confused and causes inflammation without threats being present.” Without that autoantibody piece, Crohn’s disease can’t be placed into the autoimmune disease category.
According to Dr. Dubinsky, “While a specific body system might be mainly affected, like the GI tract in Crohn’s disease, the nonspecific nature of the innate immune system means that other systems are inevitably affected as well.”
The problem with the immune system that causes IBD may also trigger other immune-mediated conditions. The risk of developing another condition is dependent upon a host of factors, including:
Some of the more common inflammatory conditions that can occur in people who live with Crohn’s disease include:
The exact mechanism of the development of Crohn’s disease is unknown, but it is thought to include several different factors. There is the genetic component, with hundreds of genes known to be associated with the condition.
Then there is an environmental trigger (or, likely, more than one) and/or a shift in the microbiome. Together, these things are thought to send the immune system into an inflammatory loop, attacking the digestive tract and other body systems.
Environmental triggers may include:
The extent to which one or more of these potential triggers is involved in a particular case of Crohn’s disease is unknown. Further, there is a lack of understanding of how the microbiome interacts with the external triggers and eventually leads to the development of disease.
There is some research showing that people with IBD have a smaller number of different species in their microbiomes.It’s thought that this lack of diversity may contribute to the development of some forms of Crohn’s disease.
Categorizing Crohn’s Disease
Categorizing Crohn’s disease is an evolving conversation. In the past, it has been referred to as an autoimmune condition. But it is now understood that it is not autoimmune because it lacks the conditions that need to be met for that classification. Crohn’s disease is more accurately described asautoinflammatory.
Some research discusses IBD as being the result of an immune deficiency. This theory points to a defect within the white cells of people who live with an IBD.However, that theory has also become less well-accepted in recent years and may not encompass the spectrum of Crohn’s disease.
It’s known that the immune system has a role in the development of Crohn’s disease. However, the understanding of how various factors interact in the development of the disease is far from complete.
It’s also thought that Crohn’s disease may actually encompass many different disorders. That could mean there are many different types of the disease as well as a spectrum of causes.
In some cases, Crohn’s disease and IBD in general are also referred to as “immune-mediated” conditions. This is a broader term that encompasses all the conditions related to the dysregulation of the immune system. As more research is completed, the understanding of what causes IBD will improve, leading to better treatments and individualized medicine.
Summary
Although people with Crohn’s disease may produce antibodies, Crohn’s disease is not considered an autoimmune disease because the antibodies they produce don’t target their own bodies.
Research is ongoing to understand the causes of Crohn’s disease and how it should be classified. There is a shift toward calling it an immune-mediated condition or an autoinflammatory condition.
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Johns Hopkins Medicine.Definition of autoimmunity & autoimmune disease.Vinh DC, Behr MA.Crohn’s as an immune deficiency: from apparent paradox to evolving paradigm.Expert Rev Clin Immunol. 2013;9(1):17-30. doi:10.1586/eci.12.87.National Institute of Environmental Health Sciences.Autoimmune diseases.Office on Women’s Health.Autoimmune diseases.Evans SS, Repasky EA, Fisher DT.Fever and the thermal regulation of immunity: the immune system feels the heat.Nat Rev Immunol. 2015;15(6):335-349. doi:10.1038/nri3843.Georgin-Lavialle S, Fayand A, Rodrigues F, Bachmeyer C, Savey L, Grateau G.Autoinflammatory diseases: State of the art.Presse Med. 2019;48(1 Pt 2):e25-e48. doi:10.1016/j.lpm.2018.12.003.Yoo JY, Groer M, Dutra SVO, Sarkar A, McSkimming DI.Gut microbiota and immune system interactions.Microorganisms. 2020;8(10):1587. doi:10.3390/microorganisms8101587.Zhao M, Burisch J.Impact of genes and the environment on the pathogenesis and disease course of inflammatory bowel disease.Dig Dis Sci.2019;64(7):1759-1769. doi:10.1007/s10620-019-05648-w.Halling ML, Kjeldsen J, Knudsen T, Nielsen J, Hansen LK.Patients with inflammatory bowel disease have increased risk of autoimmune and inflammatory diseases.World J Gastroenterol. 2017;23(33):6137-6146. doi:10.3748/wjg.v23.i33.6137.Turpin W, Goethel A, Bedrani L, Croitoru K.Determinants of IBD heritability: genes, bugs, and more.Inflamm Bowel Dis. 2018;24(6):1133-1148. doi:10.1093/ibd/izy085.Alam, M.T., Amos, G.C.A., Murphy, A.R.J. et al.Microbial imbalance in inflammatory bowel disease patients at different taxonomic levels.Gut Pathog.2020;12,1. doi:10.1186/s13099-019-0341-6
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Johns Hopkins Medicine.Definition of autoimmunity & autoimmune disease.Vinh DC, Behr MA.Crohn’s as an immune deficiency: from apparent paradox to evolving paradigm.Expert Rev Clin Immunol. 2013;9(1):17-30. doi:10.1586/eci.12.87.National Institute of Environmental Health Sciences.Autoimmune diseases.Office on Women’s Health.Autoimmune diseases.Evans SS, Repasky EA, Fisher DT.Fever and the thermal regulation of immunity: the immune system feels the heat.Nat Rev Immunol. 2015;15(6):335-349. doi:10.1038/nri3843.Georgin-Lavialle S, Fayand A, Rodrigues F, Bachmeyer C, Savey L, Grateau G.Autoinflammatory diseases: State of the art.Presse Med. 2019;48(1 Pt 2):e25-e48. doi:10.1016/j.lpm.2018.12.003.Yoo JY, Groer M, Dutra SVO, Sarkar A, McSkimming DI.Gut microbiota and immune system interactions.Microorganisms. 2020;8(10):1587. doi:10.3390/microorganisms8101587.Zhao M, Burisch J.Impact of genes and the environment on the pathogenesis and disease course of inflammatory bowel disease.Dig Dis Sci.2019;64(7):1759-1769. doi:10.1007/s10620-019-05648-w.Halling ML, Kjeldsen J, Knudsen T, Nielsen J, Hansen LK.Patients with inflammatory bowel disease have increased risk of autoimmune and inflammatory diseases.World J Gastroenterol. 2017;23(33):6137-6146. doi:10.3748/wjg.v23.i33.6137.Turpin W, Goethel A, Bedrani L, Croitoru K.Determinants of IBD heritability: genes, bugs, and more.Inflamm Bowel Dis. 2018;24(6):1133-1148. doi:10.1093/ibd/izy085.Alam, M.T., Amos, G.C.A., Murphy, A.R.J. et al.Microbial imbalance in inflammatory bowel disease patients at different taxonomic levels.Gut Pathog.2020;12,1. doi:10.1186/s13099-019-0341-6
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Johns Hopkins Medicine.Definition of autoimmunity & autoimmune disease.Vinh DC, Behr MA.Crohn’s as an immune deficiency: from apparent paradox to evolving paradigm.Expert Rev Clin Immunol. 2013;9(1):17-30. doi:10.1586/eci.12.87.National Institute of Environmental Health Sciences.Autoimmune diseases.Office on Women’s Health.Autoimmune diseases.Evans SS, Repasky EA, Fisher DT.Fever and the thermal regulation of immunity: the immune system feels the heat.Nat Rev Immunol. 2015;15(6):335-349. doi:10.1038/nri3843.Georgin-Lavialle S, Fayand A, Rodrigues F, Bachmeyer C, Savey L, Grateau G.Autoinflammatory diseases: State of the art.Presse Med. 2019;48(1 Pt 2):e25-e48. doi:10.1016/j.lpm.2018.12.003.Yoo JY, Groer M, Dutra SVO, Sarkar A, McSkimming DI.Gut microbiota and immune system interactions.Microorganisms. 2020;8(10):1587. doi:10.3390/microorganisms8101587.Zhao M, Burisch J.Impact of genes and the environment on the pathogenesis and disease course of inflammatory bowel disease.Dig Dis Sci.2019;64(7):1759-1769. doi:10.1007/s10620-019-05648-w.Halling ML, Kjeldsen J, Knudsen T, Nielsen J, Hansen LK.Patients with inflammatory bowel disease have increased risk of autoimmune and inflammatory diseases.World J Gastroenterol. 2017;23(33):6137-6146. doi:10.3748/wjg.v23.i33.6137.Turpin W, Goethel A, Bedrani L, Croitoru K.Determinants of IBD heritability: genes, bugs, and more.Inflamm Bowel Dis. 2018;24(6):1133-1148. doi:10.1093/ibd/izy085.Alam, M.T., Amos, G.C.A., Murphy, A.R.J. et al.Microbial imbalance in inflammatory bowel disease patients at different taxonomic levels.Gut Pathog.2020;12,1. doi:10.1186/s13099-019-0341-6
Johns Hopkins Medicine.Definition of autoimmunity & autoimmune disease.
Vinh DC, Behr MA.Crohn’s as an immune deficiency: from apparent paradox to evolving paradigm.Expert Rev Clin Immunol. 2013;9(1):17-30. doi:10.1586/eci.12.87.
National Institute of Environmental Health Sciences.Autoimmune diseases.
Office on Women’s Health.Autoimmune diseases.
Evans SS, Repasky EA, Fisher DT.Fever and the thermal regulation of immunity: the immune system feels the heat.Nat Rev Immunol. 2015;15(6):335-349. doi:10.1038/nri3843.
Georgin-Lavialle S, Fayand A, Rodrigues F, Bachmeyer C, Savey L, Grateau G.Autoinflammatory diseases: State of the art.Presse Med. 2019;48(1 Pt 2):e25-e48. doi:10.1016/j.lpm.2018.12.003.
Yoo JY, Groer M, Dutra SVO, Sarkar A, McSkimming DI.Gut microbiota and immune system interactions.Microorganisms. 2020;8(10):1587. doi:10.3390/microorganisms8101587.
Zhao M, Burisch J.Impact of genes and the environment on the pathogenesis and disease course of inflammatory bowel disease.Dig Dis Sci.2019;64(7):1759-1769. doi:10.1007/s10620-019-05648-w.
Halling ML, Kjeldsen J, Knudsen T, Nielsen J, Hansen LK.Patients with inflammatory bowel disease have increased risk of autoimmune and inflammatory diseases.World J Gastroenterol. 2017;23(33):6137-6146. doi:10.3748/wjg.v23.i33.6137.
Turpin W, Goethel A, Bedrani L, Croitoru K.Determinants of IBD heritability: genes, bugs, and more.Inflamm Bowel Dis. 2018;24(6):1133-1148. doi:10.1093/ibd/izy085.
Alam, M.T., Amos, G.C.A., Murphy, A.R.J. et al.Microbial imbalance in inflammatory bowel disease patients at different taxonomic levels.Gut Pathog.2020;12,1. doi:10.1186/s13099-019-0341-6
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