- IgE is a particular isotype of Antibody (see page). Production of IgE is thought to be a critical step in the pathogenesis of certain allergic responses.
- IgE is secreted as a single, free-floating antibody.
- Few immune responses result in synthesis of the IgE isotype. However, the IgE isotype is often produced in responses to parasitic infections and thus is thought to play a role in anti-parasitic immunity. Consistent with this, IgE antibodies are bound by Fc Receptors on the anti-parasitic leukocytes, Mast Cells, Basophils, and Eosinophils. Unlike other antibody isotypes, IgE is bound by its Fc Receptor even when not cross-linked with antigen. Consequently, the anti-parasitic leukocytes will possess membrane-bound IgE on their surface even in the absence of antigen.
- When antigen is present, cross-linking of membrane-bound IgE on the anti-parasitic leukocytes results in their degranulation which releases a wide variety of vasoactive and bronchoactive mediators. Inappropriate IgE-mediated degranulation to environmental antigens is thought to be the basis of certain allergic responses which is considered a Type I Hypersensitivity. In some cases, degranulation can be wide-spread and catastrophic, resulting in Anaphylactic Shock.