Remember, the host mistakenly believes this is a protective reaction. In addition, certain adhesion molecules likely have a role in inflammatory cell activation, further enhancing allergic inflammation. IgE is one of five isotypes of antibody formed in humans. Although necessary, IL-4 is not in and of itself sufficient to cause a switch to IgE. A second signal, which can come from a variety of sources, is needed to complete the switch. Once formed, IgE seeks to bind to either the inciting allergen or to IgE receptors located on a variety of cell types.
Mast cells have high affinity IgE receptors.
Of note, other cytokines are active in the regulation of IgE production. Thus IgE could be the prevalent antibody if TH2 rather than TH1 helper cells are stimulated in an atopic individual. This process takes only a matter of minutes and releases a variety of mediators, including histamine . Histamine binds to target receptors in the nose, lung, skin, gastrointestinal tract and near blood vessels via specific histamine receptors, especially H1 receptors . Mast cells themselves both respond to and produce cytokines.