Which immunoglobulin is primarily associated with Type I hypersensitivity?

Type I hypersensitivity is an allergic reaction that occurs quickly after exposure to an allergen. It is primarily mediated by immunoglobulin E (IgE). Upon first exposure to an allergen, IgE is produced and binds to mast cells and basophils. Upon subsequent exposures, the allergen cross-links the IgE bound to these cells, leading to degranulation and release of histamine and other inflammatory mediators. This process results in the classic symptoms of allergic reactions, such as itching, swelling, and bronchoconstriction.

IgA plays a vital role in mucosal immunity, IgM is primarily associated with the initial immune response and agglutination, and IgG is the most abundant antibody type in the blood, important for opsonization and neutralizing pathogens. However, none of these immunoglobulins are involved in the immediate hypersensitivity reactions characteristic of Type I hypersensitivity. Thus, IgE is specifically responsible for mediating these types of allergic responses.