Immunoglobulin E is typically the scarce isotype and is found only in mammals. It was discovered in 1966 by Teruka and Kimishige Ishizaka. IgE is a monomer showing basic structure but, with out hinge region.
Instead of hinge region IgE has an additional domain CH4. Molecular weight of IgE is 190000 Dts, and half life period is 2-3 days. The average serum concentration of IgEs is 0.3mg/ kg body weight.
IgE concentration is very high (about 50mg/ 100ml of serum) in atopic persons (people prone to allergy). The normal rate of synthesis of IgE is 2-3mg/kg body weight /day.
Carbohydrate content occupies about 12% of total molecular weight. Unlike other immunoglobulins IgE is a heat labile molecule with a sedimentation coefficient of 8 S.
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IgE binds to FC receptors of basophils and tissue mast cells. Cross linkage of receptor bound IgE with an antigen induces release of pharmacological substance from the basophiles and mast cells. The released pharmacological substances initiate allergic reaction. Hence raise in serum IgE concentration indicates allergic conditions. Even in normal individuals intestinal helminthes parasites induce raise of serum IgE levels, this rise suggests IgE role in protection against the parasites.