Which type of allergic reaction is mediated by IgE antibodies?

The type of allergic reaction that is mediated by IgE antibodies is characterized by the rapid response of the immune system upon exposure to an allergen. This process involves the binding of allergens to IgE antibodies that are attached to the surface of mast cells and basophils. Upon re-exposure to the same allergen, this interaction triggers the release of various mediators, such as histamine, which leads to immediate hypersensitivity reactions. These reactions can manifest as symptoms like urticaria (hives), hay fever, asthma, and anaphylaxis.

The other types of allergic reactions listed do not involve IgE. Delayed, cell-mediated reactions are primarily driven by T cells and occur later after exposure to the allergen. Cytotoxic, antibody-mediated reactions involve IgG or IgM antibodies and lead to the destruction of target cells but do not engage the IgE pathway. Though there are immunoglobulin-mediated reactions that might involve other types of antibodies, it is the specific role of IgE in immediate hypersensitivity that distinguishes it. Therefore, the type of reaction specifically mediated by IgE antibodies is accurately identified as an IgE-mediated allergic reaction.