Which immunoglobulin is primarily involved in Type 1 hypersensitivity reactions?

Type 1 hypersensitivity reactions, commonly known as immediate hypersensitivity reactions, are primarily mediated by IgE immunoglobulins. When an individual is exposed to an allergen, IgE is produced in response and binds to receptors on mast cells and basophils. Upon subsequent exposure to the same allergen, cross-linking of IgE bound to these cells occurs, leading to cell degranulation and the release of histamines and other inflammatory mediators. This process is responsible for the typical symptoms of allergic reactions, such as itching, swelling, and bronchoconstriction, commonly seen in conditions like allergic rhinitis, asthma, and anaphylaxis.

Thus, the significant role of IgE in initiating and propagating the response in Type 1 hypersensitivity is what makes it the correct answer in this context.