Which immunoglobulin is primarily responsible for mediating allergic reactions?

The immunoglobulin primarily responsible for mediating allergic reactions is IgE. This antibody plays a critical role in the immune system's response to allergens, which are typically harmless substances that evoke an exaggerated immune response in sensitized individuals. When an allergen enters the body, it binds to IgE antibodies that are already attached to surface receptors on mast cells and basophils. This cross-linking of IgE leads to the degranulation of these cells, resulting in the release of various inflammatory mediators such as histamine, leukotrienes, and prostaglandins, which cause the symptoms associated with allergic reactions—such as itching, swelling, and bronchoconstriction.

Other immunoglobulins, such as IgA, IgG, and IgM, have different roles in the immune response. IgA is primarily involved in mucosal immunity and protects epithelial surfaces, especially in the respiratory and gastrointestinal tracts. IgG is the most abundant antibody in serum and plays roles in opsonization, neutralization, and activating complement, while IgM is the first antibody produced in response to an infection, serving to initiate the immune response. These immunoglobulins do not have the same specific function in allergic reactions as IgE does