What is Allergy?

We will answer various questions about allergies.

Supervisor : Masahiro Sakaguchi (ITEA Director / Professor Emeritus, Azabu University)

Q1What is allergy?
A1Excessive reaction of the body to foreign substances

The human body has immunity as a defense mechanism against foreign enemies such as bacteria and viruses. Allergy is an overreaction to harmless substances (such as food). When particularly severe systemic symptoms occur, it is called anaphylaxis.

Q2What causes allergies?
A2Substances called allergens

Allergy is caused by substances called allergens. The causes of allergies vary from person to person (e.g., food, pollen, pets, dust mites, and mold). Many allergens are specific proteins contained in these causative agents.

■ Major allergens

ITEA sells the following allergens.

Q3What are the characteristics of allergens?
A3Different types of allergens have different characteristics.

Characteristics of allergen such as location, structure, and stability differ greatly for each allergen. For example, Der f 1, the main allergen in Dermatophagoides farinae that causes asthma, is abundant in mite feces and is relatively unstable to heat. Der f 2, on the other hand, is abundant in the body of mites and is stable against heat. The major allergen of Japanese cedar pollen, Cry j 1, is abundant in the pollen outer shell, and Cry j 2 is abundant in the pollen cells. The allergen does not come out when it is wrapped in the shell. However, once the pollen is exposed to conditions such as the nasal mucosa, the pollen ruptures and the allergens are released. The major pet allergens Fel d 1 from cats and Can f 1 from dogs are secreted from the salivary glands, but when the pets groom themselves, the allergens become attached to the fur or skin all over the body. Allergens are scattered around through hair and/or dander that fall out from pets.

Q4Teach me more about the mechanism of allergies.
A4IgE plays an important role in allergy.

When an allergen enters the body, B-cells having IgE antibody corresponding to the allergen recognize the allergen. T cell receives an allergen presentation from a B-cell, the T-cell orders the B-cell to make more IgE antibodies. Produced IgE antibodies bind to the surface of immune cells called mast cells and wait for allergens. When the same kind of allergen enters the body again and the allergen binds to the IgE on the mast cells, the mast cells release substances such as histamine. This causes allergic reactions such as itching, runny nose, and sneezing.

Q5IgE antibody? What is an antibody?
A5Antibodies (a.k.a. immunoglobulins) are proteins that bind to specific substances (antigens).

Antibodies are proteins that play an important role in immunity and are produced by immune cells called B-cells. An antibody has the ability to bind to a specific substance called an antigen. Among antigens, those that cause allergies are called allergens. An antibody has a Y-shaped structure. The lower part of the Y is called the constant region, and it has a fixed structure. The tips of the Y are called the variable region, and they have various structures when antibodies are produced. Owing to the structure of the variable region, antibodies bind specifically to antigens; e.g., antibody A binds to antigen a and antibody B to antigen b. Antibodies are classified into five types based on the type of constant region: IgG, IgA, IgM, IgD, and IgE. Each type has a different role in immune function. Among these five antibodies, IgE plays an important role in allergic reactions.

Q6How do you detect allergens?
A6Usually with sandwich ELISA

A method called sandwich ELISA (enzyme-linked immunosorbent assay) is generally used. Two types of antibodies that specifically react with allergens are used to detect and quantify allergens. Simple detection methods include immunochromatography.

We also sell ELISA construction kits.
Free samples are available.

Q7Can the cause of allergic symptoms be investigated by ELISA?
A7First, we recommend that you visit a medical institution.

ELISA can measure the presence or quantity of specific allergens. However, the detection of an allergen does not guarantee that it was the cause of the allergy. Causes and symptoms of allergies vary among individuals. For this reason, you should first be diagnosed at a specialized medical institution to determine which allergen is the cause of the allergy. For diagnosis, tests such as a blood test to examine IgE antibodies in blood, a patch test to visualize the reaction that occurs when allergens attach to the skin, and a provocation test to see the reactions that occur upon actual exposure to allergens will be performed.