Description: IgE is the least common serum Ig, playing a fundamental role in allergic reactions but not in agglutination or complement activation. It is found in the lungs, skin and mucous membrane. The heavy chain contains an extra domain, by which IgE attaches with high affinity to Fc epsilon Receptor I (FceRI) found primarily on eosinophils, mast cells and basophils. FceRI recognises allergens such as pollen, venoms, fungus, spores, dust mites or pet dander. Upon binding of the allergen to the IgE present on the cell, release of vasoactive amines, like histamine, or factors like heparin and leukotrienes, into surrounding tissue is initiated. Vasodilatation and increased small vessel permeability causes fluid to escape from capillaries into the tissues, which leads to the characteristic symptoms of an allergic reaction.
Most of these typical allergic reactions like mucus secretion, sneezing, coughing or tear production are considered beneficial to expel remaining allergens from the body.
Studies have shown that conditions such as asthma, rhinitis, eczema, urticaria, dermatitis, and some parasitic infections (e.g. helminths) lead to increased IgE levels. Binding of eosinophils with Fc receptors to IgE-coated helminths results in killing of the parasite. Low levels of IgE can occur in a rare inherited disease that affects muscle coordination (ataxia-telangiectasia).