Which type of hypersensitivity reaction is mediated by IgE antibodies?

A Type I hypersensitivity reaction is characterized by the involvement of IgE antibodies. This type of reaction occurs rapidly after exposure to an allergen and is commonly associated with conditions such as allergic rhinitis, asthma, and anaphylaxis. In this process, when an individual is exposed to an allergen (for example, pollen, pet dander, or certain foods), the immune system produces IgE antibodies specifically against that allergen. These IgE antibodies bind to mast cells and basophils, leading to the release of inflammatory mediators like histamine. This release causes the symptoms associated with allergic reactions, such as itching, swelling, and bronchoconstriction.

In contrast, the other types of hypersensitivity reactions involve different immune mechanisms. Type II hypersensitivity is mediated by IgG or IgM antibodies against cell surface or matrix antigens, leading to cell destruction or dysfunction. Type III hypersensitivity involves IgG or IgM antibodies that form immune complexes, which can cause tissue damage through inflammation. Type IV hypersensitivity is cell-mediated and does not involve antibodies; rather, it is mediated by T cells that respond to specific antigens. These differences underscore the specific role that IgE antibodies play in Type I hypersensitivity.