Allergy caused by dysregulation of immune response

In recent years, the number of allergy sufferers has been increasing. Hay fever, food allergy, and atopic dermatitis are examples of allergic diseases.

Why do allergies occur? They occur as a result of dysregulation of the immune response. In general, immune reactions involve complex communication between various types of immune cells using multiple signaling molecules called cytokines, which work to eliminate foreign substances in a manner best suited to the nature of the enemy. In the case of allergies, however, the immune response is misdirected against harmless substances such as pollen and food.

The direction of the immune response is influenced by environmental factors in addition to genetic factors that a person is born with. Environmental factors are thought to be deeply involved in the recent increase in the number of allergic patients.

Our research group is focusing on intestinal environmental factors such as food and intestinal bacteria as environmental factors that regulate immunity.

Regulation of allergy by metabolism of essential fatty acids

The functionality of various food components is becoming clear, and essential fatty acids are one of them. There are two systems of essential fatty acids: ω3 (omega-3) fatty acids and ω6 (omega-6) fatty acids. Linseed oil (also known as flaxseed oil or amani oil), which has been attracting attention for its health benefits in recent years, contains more than10 times the amount of α-linolenic acid, one of the ω3 fatty acids, than soybean oil which is the raw material used to make salad oil.

When experimental mice were bred with either linseed oil or soybean oil in their diets, it was found that the onset of a food allergy was suppressed in the linseed oil group. In other words, the difference in fatty acid composition in the diet determines the onset of an allergy.

As a mechanism, it was found that α-linolenic acid is metabolized by enzymes in the body and converted into an antiallergic substance, which suppresses food allergies as an effective molecule. Furthermore, through a series of studies, it has been found that rearing cattle on a diet of linseed oil reduces symptoms of arteriosclerosis and allergic rhinitis, and that there are multiple types of metabolites that act as antiallergic substances.

It has been found that the multiple antiallergic substances produced from ω3 fatty acids have different target receptors and immune cells.

This suggests that even with the same diet, if the metabolic activity of each individual differs, the type and amount of antiallergic substances produced from ω3 fatty acids will differ, resulting in individual differences in the immunoregulatory activity obtained.

Postbiotics production by intestinal bacteria

Our research group is also focusing on the production of postbiotics by intestinal bacteria. Postbiotics are functional metabolites produced by intestinal bacteria using dietary components as substrates.

Many of us have heard of the word, “intestinal flora.” It refers to the entire intestinal bacteria that live in our intestines. It is said that there are more than 100 types of intestinal bacteria and the total number of intestinal bacteria can be as large as 1,000 trillion, and they vary widely from individual to individual.

Some intestinal bacteria have unique enzymatic activities that we mammals do not have.

Certain intestinal bacteria are able to produce a substance called αKetoA (alpha KetoA) from α-linolenic acid. On the other hand, αKetoA cannot be made by mammals.

Our research group found out that αKetoA is effective against allergic dermatitis and diabetes using laboratory animals. αKetoA is also detected in human feces, but its amount varies greatly among individuals, and differences in intestinal flora may be one of the reasons for this.

From the above, in addition to the metabolic activity in our bodies, individual differences in intestinal flora may also be a factor affecting the immunoregulatory activity of ω3 fatty acids.

Toward the era of individualized/stratified nutrition for healthy longevity

Once the details of the immune regulatory mechanism of food are clarified, individualized nutrition and stratified nutrition for each type of individual are expected to be developed based on an understanding of the metabolic activity and intestinal flora of each person.

For example, some people may get enough of the desired metabolites by consuming linseed oil, while others may not. For those who do not get the desired metabolites, they can take intestinal bacterium (e.g., lactic acid bacteria) together with linseed oil. Individualized/stratified nutrition is to understand the individuality of how our body responds to what we take and provide ways to supplement what is lacking.

Finally, some people tend to eat a diet that is biased toward what they say is good for them when they hear this kind of health-related talk, but this is not a good idea. For example, ω3 fatty acids are effective in reducing allergies and inflammation, but they are not good for everything. Immune function is a double-edged sword, so to speak.

In terms of diet, it is often said that it is important to consume a good balance of various foods. Based on that, individualized/stratified nutrition needs to be achieved. We would like to promote research to contribute to healthy longevity.

* The information contained herein is current as of February 2023.
* The contents of articles on are based on the personal ideas and opinions of the author and do not indicate the official opinion of Meiji University.
* I work to achieve SDGs related to the educational and research themes that I am currently engaged in.

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