What class of antibody is prevalent in allergic and hypersensitivity reactions?

• A. IgM
• B. IgG
• C. IgA
• D. IgE

Answer: (D)

The class of antibody that is prevalent in allergic and hypersensitivity reactions is IgE. This immunoglobulin plays a critical role in the immune response to allergens. When an individual is exposed to an allergen, IgE binds to it and triggers mast cells and basophils to release histamines and other chemicals, leading to the symptoms commonly associated with allergies, such as itching, swelling, and difficulty breathing.

IgE is particularly important in type I hypersensitivity reactions, which include common allergies such as hay fever, asthma, and food allergies. This unique function of IgE in mediating these immune responses distinguishes it from other classes of antibodies, which have different roles in the immune system. For instance, IgM is the first antibody produced during an initial immune response, while IgG is more involved in long-term immunity and memory. IgA primarily functions in mucosal immunity, protecting surfaces like those of the respiratory and gastrointestinal tracts.