Tolerance, Allergies, and Hypersensitivity
Our bodies have a natural and healthy immune response to any incoming particles, from environmental particles to bacteria from external sources, and also to food. In this post I will go over a simple review of the possible ways in which our bodies respond to food particles, specifically food proteins (all foods are broken down into protein, carbohydrate, and fat - all essential for our cells to function). When we eat food, our immune system respond in one of three ways: tolerance, allergy, or hypersensitivity.
When we consume food, tolerance is the normal response in a healthy individual. What’s going on behind the scenes to create this type of response? Let’s take for example an avocado. The first time we eat an avocado, the avocado particles travel to the gut for digestion. In the gut, food is broken down into particles and presented to certain cells in our immune system (these are called T cells). When this T cell comes into contact with this avocado particle in the gut, it produces something called a cytokine, which in this case is specific for avocado. This cytokine has a special job, and its job is to trigger antibodies which will tell our body how to respond to the avocado. (For those interested, the specific cytokine produced is TGFbeta, which triggers the antibody IgA). Under normal circumstances, this antibody will tell our body to tolerate the food. The next time we eat an avocado, the body is already prepared with the right antibodies that make us tolerant to avocado, and we don’t have any adverse inflammatory reactions.
What happens when we have an allergy? Using our example above, we eat the avocado and again it travels to our gut for digestion. However, when the food particle is presented to an immune system T cell, instead of producing the cytokine mentioned above, it produces a more inflammatory cytokine (for those interested, these cytokines are IL-4, IL-5, and IL-13). These specific cytokines cause a different antibody to be presented (IgE), which is inflammatory! This antibody causes a reaction that results in redness, hives, diarrhea, swelling, pain, and anaphylaxis.
Now what happens in food hypersensitivity? Take for example someone eating bread. When the bread particles reach the gut, again they come in contact with the T cells of the immune system. In hypersensitivity, the cytokine produced is TNF alpha, which is likely the culprit in many of the food sensitivity symptoms. This cytokine causes “leaky gut” as it breaks down the tight junctions of our intestines, causes diarrhea, and causes oxidative stress in the gut. When being tested for food allergies, the cytokine and antibody measured for food allergy will not show up in the test, although clearly the food is causing our body to mount an inflammatory response. This is our link to chronic inflammation. Food hypersensitivity is likely what many people suffer from without certainty about what is causing their symptoms. It’s very difficult to test for these sensitivities without doing a strict elimination diet, and then reintroducing the foods in small amounts a little at a time until the culprit is found. But that’s for another post.
What causes the body to present a tolerant, allergic, or hypersensitivity reaction? Unfortunately, that part is not very clear. What is clear, is that these reactions are influenced by the intake of food in the first months that a child is alive (Husby, 2000). This is why breast milk is so important, it contains antibodies that help a baby develop its immune system (Brandtzaeg, 2010). It’s also important to acknowledge that food allergy isn’t necessarily more intense or dangerous than food hypersensitivity.
Husby, S. (2000). Normal immune responses to ingested foods. Journal of pediatric gastroenterology and nutrition, 30(1), S13-S19. Retrieved from:
Brandtzaeg, P. (2010). Food allergy: separating the science from the mythology. Nature Reviews Gastroenterology and Hepatology, 7(7), 380. Retrieved from: https://www-ncbi-nlm-nih-gov.uws.idm.oclc.org/linkout/pmliblink.cgi?id=20606633&lib=wscclib
Chinthrajah, R. S., Hernandez, J. D., Boyd, S. D., Galli, S. J., & Nadeau, K. C. (2016). Molecular and cellular mechanisms of food allergy and food tolerance. Journal of Allergy and Clinical Immunology, 137(4), 984-997. Retrieved from: https://www-ncbi-nlm-nih-gov.uws.idm.oclc.org/pmc/articles/PMC5030841/