Type 1 Hypersensitivity: The Overreaction of the Immune System to Allergens

How to Type 1 hypersensitivities occur?

IgEs bind to mast cells or basophils and stimulate degranulation- will release histamines, prostaglandins, and leukotrienes – later mediators will attract neutrophils and eosinophils

Type 1 hypersensitivity, also known as an immediate hypersensitivity, occurs due to an overreaction of the immune system when the body is exposed to certain allergens. This hypersensitivity occurs in response to an allergen exposure, and the process follows these steps:

1. Sensitization: During the initial exposure to an allergen, specific cells of the immune system called T-helper 2 cells become activated and produce specific antibodies called Immunoglobulin E (IgE) against the allergen.

2. Allergen Re-exposure: Upon subsequent exposure to the same allergen, the allergen binds to the IgE antibodies on the surface of mast cells and basophils in the body.

3. Release of Chemical Mediators: The allergen cross-links the bound IgE antibodies, triggering the release of chemical mediators such as histamine, leukotrienes, and cytokines. These mediators cause various symptoms such as itching, swelling, bronchoconstriction, vasodilation, and inflammation.

4. Clinical Symptoms: These chemical mediators cause the symptoms associated with type 1 hypersensitivity, which can vary based on the site of the allergen exposure. Common symptoms include itching, rash, swelling, airway constriction, hay fever, and anaphylaxis.

Therefore, the immune system inappropriately senses allergens as harmful and releases excessive levels of chemical mediators, which leads to various symptoms of type 1 hypersensitivity.

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